Heavy duty dual tire assembly

RELATED APPLICATIONS

This patent application is related to a patent application entitled “A Three Piece Tire Assembly” filed on May 31, 2001, having U.S. Ser. No. 09/871025, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to a three piece tire with a removable tread belt mounted on a reinforced tire carcass. One use of the invention is typically for use with earthmoving vehicles, others include any application where dual wheel assemblies are commonly employed.

BACKGROUND OF THE INVENTION

The heavy duty tire assembly of the present invention is generally designed for use on earthmover vehicles and are subjected to high stress and loads under harsh environmental conditions such as in rock quarries, mines, foundries, and other areas where tires are subjected to puncture-producing and wear-inducing conditions.

As discussed in U.S. Pat. No. 4,351,380, certain prior art tread belt tire assemblies comprise a plurality of ground engaging shoes spaced about the periphery of the supporting structure. The heavy loads on the shoes result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 patent is directed to an improved track belt assembly which comprise a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof

The large pneumatic tires, which are typically used for earthmoving vehicles, sometimes fail due to the high stress and loads caused by the harsh environmental conditions in which they are operated. These large prior art pneumatic tires had a greater tendency to fail in the crown or shoulder area of the tire due to excessive heat build up.

In the prior art, conventional solutions to these problems include increasing the robustness, and decreasing the tire deformation under load by increasing the sidewall stiffness. To further improve tire durability, the ply turn-up portion of these tires was typically reinforced.

With the continual drive to improve earthmover performance to severe continuous service conditions requiring 20 hours and up of service per day, seven days a week, there is a continuing need to provide novel methods and tire designs for improving earthmover tire durability. The present invention is directed to an improved pneumatic tire carcass and removable tread belt assembly with which the frequency of premature tire failure is thought to be substantially reduced. The present invention is also directed to providing an improved heavy duty dual tire assembly, which is designed to operate at long hours without damaging heat buildup. Moreover, the present invention relates to improved heavy duty dual pneumatic tires wherein a pair of removable tread belts and the tires can form an assembly which can replace conventional dual tires on any dual axle assembly including trucks, tractors, light truck vehicles, and trailers.

SUMMARY OF THE INVENTION

A heavy duty dual tire assembly has a pair of tires and two removable tread belts. The two tread belts encircle both tires. The pair of tires are coaxially aligned when mounted on rims. The rims preferably are laterally spaced dual rims commonly found on trucks and heavy earthmoving type vehicles. The rims are rigidly attached to an axle in normal use when the tires are mounted. The tires are preferably radially expandable. The tires of one embodiment of the invention are pneumatic. The tires can be provided without a ground engaging tread and without a belt reinforcing structure. Preferably the tires have at least one carcass ply. The removable tread belt is preferably a circular elastomeric cord reinforced ring. Alternatively, the removable tread belt can be made as a flat track having ends. The ends, when joined, form a circular elastomeric cord reinforced ring. The tread belt has an inner surface, the inner surface has one or more radially inwardly projecting restraining elements laterally in contact with at least one tire.

The tires have the one or more restraining elements being a single rib or a plurality of ribs or circumferentially aligned lugs positioned between the tread belt and the two tires. In another embodiment the one or more restraining elements is a plurality of grooves and tread elements wherein one or both of the tires has a circumferentially outer surface tread having tread elements and grooves that interlock with complimentary restraining elements of the tread belt.

In another embodiment, the tread belts have lateral facing surfaces abutting an annular tread belt spacer as a separate component positioned between the two tread belts and projecting into a gap or space between the dual tires.

The removable cord reinforced elastomeric tread belt has a radially outer tread, a belt reinforcing structure radially inward of the tread, and a radially inner surface wherein the radially inner surface has a lateral width sufficient to encircle a tire for normal dual wheel axles. The radially inner surfaces of the tread belts have one or more restraining elements to prevent the tread belts from slipping off the tires when mounted.

Definitions

“Apex” means a non-reinforced elastomer positioned radially above a bead core.

“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% for expression as a percentage.

“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.

“Bead” means that part of the tie comprising an annular tensile member wrapped by the ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.

“Belt or breaker reinforcing structure” means at least two layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 75° with respect to the equatorial plane of the tire.

“Bias ply tire” means a tire having a carcass with reinforcing cords in the carcass ply extending diagonally across the tire from bead core to bead core at about 25°-50° angle with respect to the equatorial plane of the tire. Cords run at opposite angles in alternate layers.

“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.

“Chafers” refers to narrow strips of material placed around the outside of the bead to protect cord plies from degradation and chaffing caused by movement of the rim against the tire.

“Chippers” means a reinforcement structure located in the bead portion of the tire.

“Cord” means one of the reinforcement strands of which the plies in the tire are comprised.

“Equatorial plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

“Flipper” means a reinforced fabric wrapped about the bead core and apex.

“Footprint” means the contact patch or area of contact o the tire tread with a flat surface under load and pressure.

“Inner line” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating gas or fluid within the tire.

“Net-to-gross ratio” means the ratio of the tire tread rubber that makes contact with the road surface while in the footprint, divided by the area of the tread in the footprint, including non-contacting portions such as grooves.

“Nominal rim diameter” means the diameter of the rim base at the location where the bead of the tire seals.

“Normal inflation pressure” refers to the specific design inflation pressure at a specific load assigned by the appropriate standards organization for the service condition for the tire.

“Normal load” refers to the specific load at a specific design inflation pressure assigned by the appropriate standards organization for the service condition for the tire.

“Ply” means a continuous layer of rubber-coated parallel cords.

“Radial” and “radially” mean directions extending radially toward or away from the axis of rotation of the tire.

“Radial-ply tire” means a pneumatic tire in which the ply cords, which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire.

“Section height (SH)” means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of the removable tread belt mounted on a pair of tires mounted on a dual rim assembly.

FIG. 2

is a cross-sectional view of a first embodiment of the invention.

FIG. 3

is a cross-sectional view of a second embodiment of the invention.

FIG. 4

is a cross-sectional view of a third embodiment of the invention.

FIGS. 5A

,

5

B and

5

C are perspective views of the removable tread belts formed in an annular ring.

FIG. 6

is a perspective view of the removable tread belt formed as a flat track.

FIG. 7

is an enlarged cross-sectional view of ends of the tread belt of FIG.

6

.

FIG. 8

is a cross-sectional view of the tire of FIG.

1

.

FIG. 9

is a cross-sectional view of the bead apex.

FIG. 10

is a cross-sectional view of a tread belt according to the embodiment shown in FIG.

2

.

FIGS. 11A

,

11

B and

11

C are portions of exemplary tread patterns for the tread belt.

DETAILED DESCRIPTION OF THE INVENTION

With reference to

FIG. 1

, there is illustrated a view of a four piece tire assembly

10

which in the specific exemplary embodiment illustrated is a size equivalent to a pair of 33.00R51 earthmover tires. At an inflation pressure of 102 psi the tire has a 119.9 inch (303 cm) maximum inflated outside diameter, a 37.2 inch (94cm) maximum inflated width tire in the axial directions, and a nominal bead diameter of 51,00 inches (130 cm). The tires are typically inflated to a pressure of about 100 pounds per square inch (psi) with air and sometimes with an air/nitrogen mixture.

As illustrated in

FIGS. 1

,

8

,

9

and

10

, the improved heavy duty tire assembly

10

includes a pair of ground engaging, circumferentially extending tread belts

12

mounted on a pair of radially reinforced, beaded tires

14

. The beaded tire

14

generally includes a pair of tire sidewalls

16

,

18

extending radially inwardly from the outer circumferential surface

20

of the tire and terminating at their radial extremities in a pair of bead wires

22

,

24

respectively, and radially inward of the maximum section width of the tire

14

. The details of the construction of tire

14

are described in detail hereinafter.

Tire

Referring to

FIG. 8

, the details of tire

14

are illustrated. The axially inward surface

28

is an inner ply liner

26

, which forms an inner liner that holds the air pressure for inflating tire

10

. The inner ply liner

26

covers the entire interior facing surface

28

of the tire

14

and serves to hold the air within the tire that is used to inflate the tire

10

. Fabric barrier plies

30

and

32

are provided within the tire in the area of the curved portion of interior surface

28

to provide support for the upper portion of the barrier rubber layer

36

and prevent the barrier rubber from being squeezed through the ply wires in the ply layer

34

. While two barrier plies

30

and

32

are illustrated, it is within the terms of the invention to use between zero and four barrier plies, as needed for a specific design.

The tire

14

also includes in its construction at least one rubberized laminated ply layer

34

of tire cord fabric which extends radially inwardly form the outer circumferential surface

20

of the tire, also called the crown area of the tire carcass, and has turn up ends

34

a

and

34

b

which wrap or loop around bead wires

22

and

24

, respectively. Although the carcass ply

34

is shown as being of single ply construction, a multi-ply construction can be employed if desired. Preferably, the carcass ply

34

is made of a rubberized ply of steel cord, but it can be made of a non-steel carcass reinforcing material.

At the radially outermost portion of the tire

14

there is a thin layer of abrasion resistant tread compound

81

. The abrasion resistant tread compound

81

forms a tough durable long wearing surface between the tread belt

12

and the tire

14

. The use of tread rubber is an ideal material because it is adapted to form a durable wear surface as shown in

FIG. 3

, ribs

76

and grooves

78

, may be used to retain the tread belt

12

. Preferably the tread compound

81

is identical to the rubber compound used in the tread belt

12

, which is also generally a typical rubber blend used for treads.

Between the inner liner

26

and the ply layer

34

is a barrier rubber layer

36

, which backs up the entire length of ply

34

and is formed of a soft compound of rubber which squeezes against the ply layer

34

. Annular stiffeners, known as apexes or apes elements

38

,

39

herein, each having a generally triangular shape are provided radially outward of the bead wires

22

,

24

respectively, and between the barrier rubber

36

and the inner liner

26

. The apexes

38

,

39

extend from approximately the mid-sidewall and the area of the inner liner

26

radially outward from the bead wires

22

,

24

respectively, or stiffening the bead area to help prevent the tire from bending over the flange

35

. Axially outward from apexes

38

,

39

and between the ply layer

34

where it turns up about bead wires

22

,

24

are located lower gum chafers

40

,

41

respectively, that support the bead wires

22

,

24

respectively, in the area of the wheel mounting rim

42

and to prevent chafing of the tire by an adjacent wheel mounting rim. Upper gum chafers

44

,

45

are disposed against the lower gum chafers

40

,

41

respectively, and the lower tire sidewalls

16

b

,

18

b

respectively to provide support for the bead wires

22

,

24

in the area of the flange

35

and to prevent chafing of the tire by an adjacent wheel mounting rim.

Between lower chafers

40

,

41

and the rubber barrier

36

in the area partially surrounding bead wires

22

,

24

are located fabric or wire chafer plies

46

,

47

that support the bead wires

22

,

24

respectively. As best seen in

FIG. 9

, the chafer plies

46

are primarily disposed against the inner facing surfaces of lower chafers

40

,

41

. Between the inner surface of ply layer

34

and the bead wires

22

and

24

are located flippers

48

,

49

respectively, which are reinforced fabric materials that are wrapped about the bead core and at least a portion of one of the apexes. On either side of the ends

34

a

,

34

b

of ply layer

34

are two wire coat, gum layers

50

and

52

which cover the ends

34

a

,

34

b

of ply layer

34

are two wire coat, gum layers

50

and

52

which cover the ends

34

a

,

34

b

of ply

34

and enable the movement of ply

34

between the gum layers

50

and

52

without exposing the wire within ply

34

during tire construction or severe bending of the tire.

Apex Configuration

Two annular stiffeners, referred to as apexes

54

,

55

herein, each having a generally four sided shape, are provided radially outward of the bead wires

22

,

24

respectively, between flippers

48

,

49

and out to apexes

58

,

59

for stiffening the area about the bead wires

22

,

24

respectively, to help prevent the tire from bending over the flange

35

. The apexes

54

,

55

are further disposed between the lower inner end of rubberized ply layer

34

and the turn-up ends

34

a

and

34

b

. Abutted against and extending radially outward from the apexes

54

and

55

are two annular stiffeners, referred to herein as apexes

58

and

59

, respectively, which help support the ends

34

a

and

34

b

of the rubberized ply layer

34

. The apexes

54

,

55

are constructed of a relatively hard compound having a modulus of about 12.2-14.9 megapascals/cm

2

at 200% elongation. Axially outward from the apexes

58

and

59

are the outer apexes

62

and

64

respectively. The apexes

38

,

39

,

58

,

59

, and

62

,

64

are generally constructed of the same relatively soft rubber compound having a modulus of about 7.2-8.8 megapascals/cm

2

elongation and act to provide a soft cushion that absorbs the stresses around the turn up ends

34

a

and

34

b

of the ply layers

34

which is caused by stress forces generated by the flexing of the tire. While the apexes

38

,

39

,

58

,

59

and

62

,

64

are typically constructed of the same rubber compound, it is within the terms of the invention to construct one or more of the apexes with a different modulus within the range of between about 7.2 and 8.8 megapascals/cm

2

at 200%. In the preferred embodiment, the apexes

38

,

39

,

58

,

60

,

62

and

64

are softer than the apexes

54

and

55

, which are located directly adjacent, and radially outward form the bead wires

22

and

24

, respectively. Preferably the rubber compound used to form the apexes

54

and

55

are about 20% to about 50% an preferably about 20% to about 50% stiffer than the rubber compound used to form apexes

38

,

39

,

58

,

59

,

62

and

64

.

The location of the ply turn-up ends

34

a

and

34

b

are an important aspect of the tire design. As is illustrated in

FIG. 9

, preferably the turn-up ends

34

a

,

34

b

are located radially outward a distance of between about 2 and 3 bead diameters from the intersection of a centerline

66

which extends through the center of bead wires

22

,

24

and a line

67

which is tangent to the most radially inward surface of the carcass ply

34

where the carcass ply portions

34

a

,

34

b

loop around the wire beads

22

,

24

to a line

68

which is perpendicular to centerline

66

and is tangent to the outer end of the ply layer

34

. This location of the outer ends of the turn-up ends

34

a

,

34

b

of ply layer

34

is important in that it can with stand the pressure exerted against the ply end, which was sometimes sufficient to cause the ply end to break through the sidewall in prior art constructions where the turn-up ends extend closer to the center of the tire sidewalls. The advantage of having the outer ends of the turn-up ends

34

a

,

34

b

of carcass ply

34

at a lower position closer to the radial outward portion of the flange

35

is so that when operating conditions cause the ply end to break through the sidewall in prior art constructions where the turn-up ends extend closer to the center of the tire sidewalls. The advantage of having the outer ends of the turn-up ends

34

a

,

34

b

of carcass ply

34

at a lower position closer to the radial outward portion of the flange

35

is so that when operating conditions cause the tire to deflect outwards, the ends of turn-up ends

34

a

,

34

b

of the play layer

34

will be supported by flange

35

. This arrangement will greatly reduce the possibility that the outer ends of turn-up ends

34

a

,

34

b

will be the cause of a crack in or penetrate axially outward through the sidewall of the tire

14

.

The ply line of ply layer

34

follows the natural ply line, which means it is already at its natural shape upon inflation. The carcass ply

34

retains its natural shape when inflated to reduce the inflation strain on the tire. The portion of the ply cord extending down to the beads

22

is equally supported along its length by the axially interior surface

37

of the rim flange

35

which is substantially parallel to the centerline

66

passing though beads

22

,

24

.

Tread Belt

The tire

14

as illustrated does not require a tread or belt reinforcing structure because those components are provided in a removable tread belt

12

described below.

The ground engaging, circumferentially extending tread belts

12

are removably mounted on the pair of tires

14

. As best shown in

FIGS. 3 and 10

, the underside or inner circumference surface

70

of tread belt

12

may have a plurality of annular ribs

72

and grooves

74

that mate with ribs

76

and grooves

78

of one or both tire

14

to restrain belt

12

from lateral or axial movement with respect to the tires

14

.

As shown in

FIG. 10

, the tire tread belt

12

includes a tread portion

15

and a belt reinforcing structure

100

having a plurality of tread belts

84

,

86

, and

88

. A radially inner belt layer

84

and

86

have cords of steel having a core strand surrounded by sheath strands. The core strand preferably has a plurality of three filaments forming the core. The wire construction is as described in co-pending application Ser. No. 09/507,316, filed Feb. 18, 2000, entitled STEEL CORD FOR REINFORCING ELASTOMERIC ARTICLES, which is incorporated by reference herein in its entirety. Each tread belt layer

84

,

86

have the cords oriented at an angle of 15° to 80° relative to the circumferential direction and spaced at 4 ends per inch. These adjacent layers

84

,

86

being equal but oppositely oriented.

The radially outermost third layer

88

has the steel cords oriented at 90° relative to the circumferential direction. This in combination with the belt layers

84

,

86

create a very strong construction. Radially inward of these belt reinforcement layers is a unique first reinforcement layer

90

having cords

92

oriented 0° relative to the circumferential direction, preferably spaced at 3 EPI, all of these layers

84

,

86

,

88

and

90

forming the structure

100

.

While three tread belts layers

84

-

88

is illustrated, it is within the scope of the invention to use other numbers of tread belt layers as needed. The combination of a removable tread belt

12

with a pair of tires

14

for use the large earthmoving vehicles is important in that it enables a portion of a three piece tire assembly

10

to be replaced instead of the entire two tires in the event the tires are fully worn, i.e., the tire belt

12

of one of the tires

14

, wears out before the other parts. Also, it may be desirable to have different types of tread designs such as, for example, driving or steering tread designs. This feature allows for a less expensive means of changing the tire tread to construct the appropriate style of desired tire. This feature greatly reduces the cost of storing spare tires and could even extend the operating time of the tires.

A unique aspect of the present invention is the provision of zero degree wires

92

in the first reinforcement layer

90

. The zero degree wires in layer

90

encircle the tire tread belt

12

and are provided to restrict the radially outward growth of the tread belt

12

which otherwise could occur due to a serious deflection in the tire carcass. By keeping the tire tread belt

12

from expanding radially outward, the tire's tread will maintain a more flat tread profile, which will improve the tread life and durability. The zero degree

92

wires in first reinforcement layer

90

eliminates the need for a larger number of belt layers.

With particular reference to the first reinforcement layer

90

it is believed most beneficial to have the axially outermost cords

92

axially inward of the lateral ends of the belt layers

84

and

86

. As shown the lateral ends of the belt layer

84

overhangs the adjacent first reinforcement layer

90

and project axially outward from the lateral ends of belt layer

86

. By insuring the belt layers

84

and

86

overhang or extend beyond the zero degree cords

92

of the first reinforcement layer

90

provides added protection against cut damage of the cords

92

. As can be easily appreciated as a large sharp rock is rolled over in the path of the tread belt, the lateral ends of the tread belt can deflect and the belt layers

84

,

86

by overhanging actually can bend over the zero degree cords

92

stopping the rock form cutting those cords.

The primary advantage of the tread belt design in the region of the lateral edges is the fact that the lateral edge portions of the tread belt

12

at the surface adjoining the circumferentially outer surface of the carcass

14

extend beyond the carcass

14

as shown at the interface

20

of the tread belt

12

and the carcass

14

. This increases the flexibility of the tread belt

12

and improves the handling characteristics of the tire

10

. The outer surface of the tread has an inclination of &thgr;, &thgr; being about 4° slope in the lateral portions of the tread and is flat or 0° sloped in the central region. The flat shaped central region extends at least 50% of the total tread width. In the 31.00R51 design, the central portion extends over 24.00 inches and each lateral portion extends from the central portion 25% or less of the total tread width, or about 7.00 inches in the 31.00R51 tire size of the illustrated embodiment tire.

This transition of the tread surface in the region Lo from sloping flat 0° to a 4° radially inward slope creates a shoulder drop-off (D) of at least 10 mm. This feature lowers the tread belt

12

contact pressure in the lateral portions and this generally reduces the shoulder wear particularly in the steering wheel positions. An added benefit is noted that in the deflection of the lateral portion is enhanced by a reduction in the radial height of the tread created by the shoulder drop-off (D). This means that the thinner tread at the lateral ends is easier to deflect radially outwardly but almost paradoxically the amount of inward pressuring trying to deflect inwardly the tread edge is lowered by the sloping shoulder. In combination this insures that while the tread belt is deliberately made flexible at the lateral edge to accommodate large stones and rock, preferably, the entire central region of the tread has even footprint pressures at the crown wherein the tread is fully supported. Ideally, the footprint pressure at the shoulders of the tread is equal to, or slightly less than, the central region.

At the interface between the tires

14

and the tread belt

12

it is believed desirable that the tread belt

12

overhangs the inflated an unloaded tires by an amount of at least 15 mm or 2% of the combined tires width as measured at the interface

20

. As the heavy duty dual assembly

10

is placed under normal load the tires

14

expands radially outwardly to a location almost aligned with the lateral end of the tread belt

12

at the lateral end of the axially outer or exterior sides of the pair of tires. It is believed less desirable to have the tires

14

at the tread belt

12

interface to be extending laterally outward of the tread belt

12

. The subtle relative movement of the tread belt

12

to the tires

14

means that to insure the outer sides of the tires

14

are not exposed requires the tread belt

12

to actually overhang the tires

14

at the interface. While large amounts of overhang may be feasible it is considered inefficient to allow the tread belt

12

to extend beyond the maximum section width of the tires on the outside of each dual wheel assembly. This is true for several reasons, first being each

1

inch of axial tread belt width on large sized tires such as 31.00R51 tire weighs approximately 100 lbs., secondarily the tread thickness is about 5.00 inches or greater and the distance to a location of the maximum section width of the carcass is another 24 inches meaning the rocks and debris most likely to damage the tire

14

will strike at the tread belt interface. Rocks

30

inches or greater simply are too unlikely to be traversable in the quarry and therefore create no realistic threat to carcass damage, thirdly because the present invention has the lateral edges to be of reduced stiffness to facilitate some degree of deflection radially inwardly, too large of an unsupported overhang could lead to flexure fatigue in the first reinforcement layer

90

requiring stiffening of the tread belt as was done in the prior art patent U.S. Pat. No. 4,050,495.

It is apparent that there has been provided in accordance with this invention apparatus and methods for constructing an improved heavy duty tire assembly

10

with a pair of removable tread belts

12

wherein the tire durability has been substantially increased. The improved tires and removable tread belts form a heavy duty assembly allowing large tires to be transported in several sections and then assembled at the delivery site. Further, the removable tread belt assembly allows a different tread belt

12

having alternative tread patterns as shown in

FIGS. 11A

,

11

B and

11

C (for exemplary purposes), to be applied to the pair of tires

14

so as to alter the driving characteristics of the tire assembly quickly and economically.

The heavy duty dual tire assembly

10

as described in the preceding pages is an example of one embodiment of a tire assembly having a pair of removable tread belts

12

and a pair of tires

14

.

With reference to

FIG. 1

, the tire assembly

10

is shown in the perspective view. This tire assembly

10

shows the tread belts

12

having a radially outer tread

15

and internal of the tread belts

12

are two tires

14

which are encircled by the annular ring formed by the tread belts

12

. As shown, the tires

14

are mounted on a dual rim

2

. The tires

14

may employ a tread at the circumferentially outer surface having grooves

78

and ribs

76

that will assist in restraining the tire

14

and tread belt

12

from slippage either laterally or circumferentially. Additionally, these ribs

76

and the rib

8

of the tread belt

14

may be provided with sub passages

80

for convective air cooling maintaining both the tread belt

12

and the tire

14

in a cooling position preventing excessive heat buildup as illustrated in

FIG. 5B

of the tread belt

12

.

With reference to

FIG. 2

, a cross-sectional view of the heavy duty dual tire assembly

10

is shown. The two tires

14

are shown mounted on a dual rim assembly

2

radially outward of the two tires

14

and encircling the tires

14

is the pair of tread belt assemblies

12

. Located approximately mid-way between the two tires

14

the pair of tread belts

12

are shown abutting along the lateral edges

75

,

77

of the tread belts

12

. This abutting along the interior lateral edges

75

,

77

of the dual tire assembly

10

prevents the tread belts

12

from deflecting radially inwardly and also provides additional circumferential slippage resistance. As shown, surface of the lateral edges

75

,

77

of the tread belt

12

can be smooth or axially aligned, which increases the contact area with the lateral surface

75

,

77

of the other tread belt

12

. Once the first tire

14

and the tread belt

12

are mounted, the second tire

14

and tread belt

12

can then be mounted onto and shoved up against the lateral surface

77

of first tread belt

12

completing the tire assembly

10

in a rather simple and straightforward fashion. It must be appreciated that these tread belts

12

can come in sizes in excess often foot in diameter and weigh several tons. Therefore, a simple means for assembling the tread belts

12

and tires

14

on the very large earthmover vehicles is desirable.

With reference to

FIGS. 2 through 4

, in each embodiment shown the restraining means for the tread belts

12

are provided by a series of circumferentially continuous grooves

74

or ribs

72

which can interlock with the grooves

78

and ribs

76

shown on both of the tires

14

. It must be appreciated that the tread belt

12

is simply laterally restrained by these grooves

74

,

78

and ribs

72

,

76

thereby keeping the tread belt

12

from slipping off of the tires

14

. It has been determined circumferential restraining of the tread belt

12

and tires

14

is not necessary due to the maximum amount of surface contact at the inner surface

8

between the tires

14

and the tread belt

12

. Nevertheless, it is feasible to provide such interlocking features to prevent circumferential torque from causing any slippage.

In the alternative embodiment of

FIG. 3

, the lateral edges of the tread belts

12

are shown having interlocking ribs extending radially outwardly along the abutting lateral edges

75

,

77

. These interlocking ribs

71

can be provided on each lateral surface of the tread belts

12

for symmetry and simplified mold manufacturing. These interlocking ribs increase the surface area of the abutted tread belts and therefore provide increased deflection stiffness.

In each of the embodiments of figures two and three the abutted tread belts

12

although being radially unsupported in the gap

200

between the two tires

14

are actually not cantilevered in such a way to permit excessive deflections. This is true because the abutting lateral

75

or

77

surface of the opposite tread belt

12

creates a compressive force as one tread belt

12

tries to deflect the opposite tread belt

12

presses against the deflecting tread belt restraining the deflection. In fact, the abutting tread belts

12

act as though they are a beam supported at both ends by the two tires. This novel way of supporting an independent and otherwise unsupported beam was a critical feature in bridge construction and in arches generally wherein the other members of the arch support the load by being in contact with adjacent pieces of the arch.

This is an important concept in this type of dual tire assembly

10

. As shown the tread belts

12

are abutted. In fact, small gaps can be tolerated between the tread belts

12

along the adjacent lateral edges. The reason gaps are permitted is the tread belts

12

as they roll into the tires footprint actually radially compress the tread rubber, which effectively closes the tread gap distance. Secondarily, the radial deflection under a load on one or both belts slightly bends the tread belts at the lateral edge causing an abutting contact to occur. Accordingly, when the present invention describes the opposing tread belt

12

as being abutted it means that under deflected load in the tires footprint the tread belts should come into supporting contact to prevent excessive radially inward deflection. Otherwise the tread belts

12

can actually be slightly gapped when the wheels are unloaded or out of the tire's footprint.

As shown in

FIG. 4

, another embodiment of the invention is shown wherein the assembly

10

is provided with a central circumferentially continuous tread belt spacer

9

interposed between the tread belts

12

and the two tires

14

, the tread belt spacer

9

is positioned between the two tires

14

and is a separate piece that may be formed in an annular shape such that it can lock onto the adjacent lateral edges

75

,

77

of the tread belts

12

. Once the tires

14

are mounted and inflated, the compressive forces between the tires

14

and the tread belt

12

lock the spacer

9

in such that lateral movement of the tread belt

12

is prevented.

As illustrated the spacer

9

can be a circumferentially continuous ring having an outer tread

15

and a reinforcing belt structure

100

similar to that described in the tread belts

12

. Several belt layers

84

,

86

,

88

and a zero degree restrictor layer

90

are shown radially inward of the belt reinforcing structure is a radially inner rubber portion. The tread belts as shown have symmetrical amounts of overhang sufficiently large enough to permit the spacer

9

to interlock with both adjacent lateral edges of the two tread belts

12

. The spacer

9

effectively spans the gap between the dual mounted tires.

As in the previously described embodiments, the spacer

9

in combination with the two tread belts

12

provides a means to limit the radial inward deflection of the tread belts in the central region of the assembly

10

. In this embodiment, the tread belts

12

are symmetrically mounted over the tires

14

and the amount of overhang is identical on both sides of the tires. The spacer

9

simply occupies the gap.

In each of the embodiments shown, the central portion of the dual tire assembly is covered by a tread belt

12

and a spacer

9

. As shown these features prevent the entry of large stones or other debris, which can become lodged between the tires.

Prior to the present invention massive steel rods known as “stone and rock ejectors” were rigidly mounted to the frame of the vehicle and located between the tires to pry the stones loose to prevent them from becoming permanently lodged between the tires. The present invention eliminates the need for such structures as no space is provided for rocks to become captured between the tires.

With reference to

FIGS. 5A

,

5

B and

5

C perspective views of the tread belts

12

are shown where the tread belt