Non-pneumatic spare tire

FIELD OF THE INVENTION

This invention relates to an improved non-pneumatic tire that can be used primarily as a temporary spare tire. The improved tire is designed to replace the conventional pneumatic spare tire.

BACKGROUND OF THE INVENTION

Non-pneumatic tires are old in the art. Non-pneumatic solid rubber tires were in use prior to pneumatic tires. As vehicle speeds increased and ride characteristics became more important the need for a better tire structure emerged. The invention of the pneumatic tire provided a solution to the problems and limitations of solid tires.

The pneumatic tire is an efficient structure that has endured as a solution to conventional vehicle requirements. A pneumatic tire is a “tensile structure”. Tensile structures always contain a compression member for providing a tensile preload in the tensile member. The tensile member can usually accept no compression and the compression member no tension. In pneumatic tires the cords are the tensile members and the compressed air is the compression member.

The primary drawback of a pneumatic tire is that it is pneumatic. Air contained under pressure can and usually does escape at the most inopportune times at least from the driver's viewpoint. It is aggravating to find that the spare tire that has been stored in the trunk for years is also flat.

The present invention has no air under pressure. It is a tire structure that performs similarly to a pneumatic tire without requiring pressurized air.

SUMMARY OF THE INVENTION

The present invention is a non-pneumatic tire comprising a rim and one or more elastomeric materials bonded to the rim or to one another. The tire has an equatorial plane, an annular tread, and an annular elastomeric body having first and second spaced lateral sides equidistant from the equatorial plane and extending between the tread and the rim. The tire body has a plurality of equally spaced arches forming at least a first series of openings extending from the first side to the second side. The first openings having a height at least one-half the height of the tire side.

In one aspect of the invention, each arch of the non-pneumatic tire has a constant radius of curvature.

In another aspect of the invention, the arches form a second series of openings circumferential and radially offset from the first openings. The second openings preferably have a triangular shape due to the arch configuration.

In another aspect of the invention, the first openings have a height of one-half to three-quarters of the tire side.

In another aspect of the invention, the openings in the non-pneumatic tire extend the fill width of the body. The openings may also vary in size across the width of the body.

Definitions

The invention also may be better understood in the context of the following definitions, which are applicable to both the specification and the appended claims:

“Axial” and “axially” are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire;

“Elastomer” means a resilient material capable of recovering size and shape after deformation;

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

“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load;

“Normal load” refers to the specific design load for the service condition for a tire;

“Pneumatic tire” means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric, and steel or other materials;

“Radial” and “radially” are used to mean directions radially toward or away from the axis of rotation of the tire;

“Rim” means a support for a tire or a tire and tube assembly upon which the tire is secured; and

“Tread” means a molded rubber component which, when bonded to a tire body, includes that portion of the tire that comes into contact with the road when the tire is under normal load.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference to the accompanying drawings in which:

FIG. 1

illustrates an annular non-pneumatic tire of the invention without rim;

FIG. 2

illustrates a side view of the tire of

FIG. 1

attached to or bonded to a rim;

FIG. 3

is an enlarged cross-sectional view of the tire and rim taken along lines

3

—

3

of

FIG. 2

;

FIG. 4

is a side view of a portion of the tire and rim;

FIG. 5

is a side view of a portion of the tire and rim under a normal load illustrating the deflection of the tire;

FIG. 6

illustrates an embodiment of the non-pneumatic tire; and

FIG. 7

illustrates another embodiment of the non-pneumatic tire.

DETAILED DESCRIPTION OF THE DRAWING

With reference to

FIGS. 1-3

, a tire

10

has an annular body

12

, which includes first and second sides

14

,

16

respectively. Each side

14

,

16

is equidistant from the equatorial plane and extends radially inwardly from the tread

18

and radially outward from the base

20

. Between the tread

18

and the base

20

are a plurality of arches

22

forming a series of repeating primary openings

24

and a series of secondary openings

26

radially and circumferentially offset from the primary openings

24

. In the illustrated tire

10

, there are twenty-four primary openings

24

and twenty-four secondary openings

26

.

A circumferential rib

28

is integrally molded into the body

12

and extends radially inwardly of the base

20

of the annular body

12

. The rib

28

assists in fixing the annular body

12

to a rim

30

.

In

FIG. 2

a side view of the tire

10

, including a rim

30

, is illustrated.

FIG. 2

further illustrates the arches

22

forming the primary openings

24

and the secondary openings

26

. The arches

22

extend from one side

14

of the tire to the other side

16

, so that the openings

24

,

26

extend through the thickness of the width of the tire

10

. The primary openings

24

have a height, relative to either side

14

,

16

of the tire

10

, of at least one-half the tire side

14

,

16

height. As illustrated, the height of the primary openings

24

is approximately three-fourths of the side height. If the opening

24

is too small, the tire

10

fails to provide enough resiliency during use; conversely, if the opening

24

is too large, than there may be insufficient material to permit the tire

10

to operate as desired.

As shown in

FIG. 3

, the rim

30

is radially inward of the annular body

12

. The mating surfaces of the rim

30

and annular body

12

are adhesively jointed. The rib

28

is interlocked with a circumferential groove

32

in the rim

30

. This mechanical rib

28

assists in locking the annular body

12

to the rim

30

.

Additionally, while not illustrated, the base

20

may be reinforced with inextensible reinforcing members. The reinforcing means can be individual wire filaments, individual cables, or wrapped steel cables. The selection of a reinforcing material will be dependant upon the material selection for the body

12

and upon the any desired strengthening of the body

12

. The inextensible reinforcing members assist in preventing growth of the body

12

during rotation. Such an option is dependant upon the material selection for the body

12

and is preferably used only when the body

12

is formed of more resilient materials that may be subject to greater deformations while under operation.

FIG. 4

illustrates just a portion of the tire body

12

, showing the configuration of the arches

22

and formed primary and secondary openings

24

,

26

. For each arch

22

, the maximum radial height of the arch

22

is closest to the tread

18

.

The inner side of each arch

22

is defined by a first radius R

1

that defines the majority of the inner side of the arch. A second radius R

2

defines the portion of the arch radially inward where each arch

22

connects with the adjacent arch

22

. Each second radius portion connects with a relatively flat base

25

of the primary opening

24

. Each primary opening

24

may also be geometrically described as an arc joined by a chord wherein the connection points between the arc and the chord are rounded out.

The outer side of each arch, having a radius R

3

, forms the two lower sides of the three sided secondary opening

26

. The secondary opening

26

may be geometrically described as an inverted triangle with the junctures between the three legs being rounded out. To minimize the stress on the three junctures, the junctures are all preferably formed with the same radius of curvature R

4

.

The radius of each arch

22

is identical to allow for equal load sharing. The dimensions of the radii, the resulting thickness of the individual arches

22

, the number and size of the arches

22

is based upon a number of factors, including, but not limited to, the material selection for the body

12

, the circumferential length of the body

12

, the anticipated load characteristics, and desired operating conditions.

Because of these factors, some of which may be excluded when designing the body

12

, and the flexibility of the arch design, for a single tire size, a variety of bodies with different arch dimensions can be designed. For example, when using a more resilient material, the arches may be relatively thicker resulting in fewer number of primary openings

24

, while when using a less resilient material, the arches may be relatively thinner resulting in a larger number of primary openings

24

.

FIG. 5

illustrates the tire

10

under a loaded condition. The area

32

in contact with the road surface defines a contact path or footprint. Radially inward of the contact path, the annular body

12

is compressed. When the body

12

is compressed, the arches

22

flex down, transferring the weight down the sides of the arches

22

to the base

20

and the rim

30

. As seen, the arches

22

flexes downward, instead of collapsing or buckling as an internal column type support would.

An alternative embodiment of the annular body

12

is illustrated in FIG.

6

. This is a cross sectional view similar to the lower portion of FIG.

3

. However, in this embodiment, the width of the primary opening

24

, from each side

14

,

16

of the body

12

decreases as approaches the equatorial plane of the body

12

. This embodiment provides more material at the equatorial plane of the body

12

.

Another embodiment is illustrated in FIG.

7

. In this embodiment, the size of the primary opening

24

decreases as it approaches the equatorial plane from each side of the body

12

, and maintains a constant diameter at the central portion of the body

12

.

The secondary openings

26

may also have varying widths similar to the primary opening

24

embodiments of

FIGS. 6 and 7

. Alternatively, the secondary openings

26

may be entirely eliminated from the body

12

.

Also, to vary the ride characteristics of the tire

10

, either the primary or secondary openings

24

,

26

may be completely or partially filled with a foam rubber.

While the arches

22

, and the corresponding formed primary and secondary opening

24

,

26

are illustrated as extending straight across the transverse width of the tire, the openings

24

,

26

may be in a variety of configurations. The openings

24

,

26

may extend obliquely across the tire width, may be curved across the tire width, or may be v-shaped across the width. By varying the orientation of the openings

24

,

26

, and thus the orientation of the arches

22

, under load the openings

24

,

26

will progressively collapse and at no time will the load be completely on one single arch

22

, but will be further distributed over adjacent arches

22

.

In the preferred embodiment, the tread portion

18

comprises a first resilient material and the body

12

comprises a second resilient material.

The annular body

12

is comprised of a material having a Young's modulus E from about 21 to about 21,000 Kg/cm

2

. For use as a temporary spare tire for passenger vehicles, it is preferred to use an elastomeric material having a Young's modulus E from about up to 421 Kg/cm

2

with a more preferred range being from 105 to less than 351 Kg/cm

2

. The preferred tensile modulus at 300% is 161 Kg/cm

2

or 915.9 MPa's.

A Young's modulus E greater than 140 Kg/cm

2

may require a mixture of polyurethane and chopped fibers of an aromatic polyamide. One form of elastomeric material which is believed to be preferred especially for tires is polyurethane. In the preferred embodiment the annular body is made from an isocyanate terminated polyester with a Shore hardness of 87A, a % NCO content of 6.8 and a 100 degree Celsius viscosity of 740 MPa.s.

While a Shore A hardness of between 60 and 100 is desired for the body

12

and 25 to 70 for the tread, it is preferred that the tread be in the range of 55 to 65 and the body in the range from 80 to 95 for passenger spare tires.

The tread material can be made from any conventional compound used in passenger tires, such as natural rubber, SBR, polybutadiene, or blends of these compounds.

The rim

30

could be made from steel, aluminum, or other metal alloys. Alternately it could be made from reinforced synthetic composite materials. One example of a suitable material is a non-oriented fiber reinforced resinous composite materials; specifically, glass reinforced vinyl ester.

The tire

10

may be manufactured by several acceptable manufacturing processes. Specifically, the annular body

12

may be molded in a mold utilizing liquid injection of the urethane from the bottom, or the urethane material can be poured into the mold from the top, thus filling the mold cavity, or thirdly the urethane may be added to a mold and spin cast to form the annular body

12

.

The body

12

can be molded directly onto the rim utilizing any of the three above-mentioned processes. Alternatively, the body

12

can be adhesively fixed to the rim

30

as a secondary operation. In either case, the rim

30

must be cleaned and an adhesive coating applied to the rim

30

to ensure adequate bonding of the rim

30

to the body

12

of the tire

10

.

The annular body

12

is buffed along the surface to which the tread layer is to be mounted. After buffing the surface, adhesive is applied. After preparing the body

12

with adhesive, a green rubber strip of material is layered onto the prepared surface of the body

12

, the unvulcanized material to be formed into the tread

18

of the tire

10

after molding.

The assembly is placed in a conventional mold. The tire

10

is cured at a temperature of about 149° C. for one hour. The mold provides compression to the assembly and forms the tread

18

that is vulcanized directly on the annular body

12

. The tire

10

and rim

30

assembly is then removed from the mold. The urethane body

12

requires aging after manufacture. In the preferred embodiment the annular body is aged at 121° C. after curing and bonding the tread to the tire assembly.

An alternative method of manufacture of the urethane body

12

simplifies the manufacturing process. In an alternative method of manufacture, a rim

30

and a prepared precured tread

18

are placed into the mold for forming the annular body

12

. The body material is injected into the cavity, thus bonding directly to the tread

18

and the rim

30

. The complete tire assembly is removed from the mold. The tire assembly is then aged at 121. degree. C. for 12 hours. After aging the tire

10

is ready for use.

As discussed, by providing the body

12

with arches

22

, the arches

22

flex and compress with load, transferring forces to the wheel rim

30

. The flexing of the arches

22

reduces harshness of the tire

10

as the tire

10

rotates through the footprint. Also, the design of the arch

22

provides for great flexibility in the exact design of the tire body

12

.

Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the fill intended scope of the invention as defined by the following appended claims.