US 20090301625 A1
A non-pneumatic tire for a vehicle featuring a body of elastic material and having a circumferentially-extending crown portion featuring a running surface and circumferentially-extending sidewalls joined to the crown portion. The side walls terminate in circumferentially-extending beads which are adapted to engage the rim of a vehicle wheel. A number of radially-extending and circumferentially-spaced compound-curve springs made of a composite material are at least partially embedded within the crown portion and the sidewalls. The curved springs have ends terminating within the beads of the tire body. A circumferentially-extending belt constructed of a high-strength and low stretch material is positioned radially outside of the compound-curve springs.
1. A non-pneumatic tire for a vehicle comprising:
a. a body made of an elastic material and having a circumferentially-extending crown portion featuring a running surface and circumferentially-extending first and second sidewalls joined to said crown portion, said circumferentially-extending first and second side walls terminating in circumferentially-extending first and second beads, respectively, said first and second beads adapted to engage a rim of a vehicle wheel; and
b. a plurality of radially-extending and circumferentially-spaced springs constructed of a composite material at least partially embedded within said crown portion and said first and second sidewalls of the tire body, each of said composite springs having a first end terminating within the first bead of the tire body and a second end terminating within the second bead of the tire body.
2. The non-pneumatic tire of
3. The non-pneumatic tire of
4. The non-pneumatic tire of
5. The non-pneumatic tire of
6. The non-pneumatic tire of
7. The non-pneumatic tire of
This application is a divisional of U.S. patent application Ser. No. 11/123,808, currently pending, which is a continuation-in-part of U.S. patent application Ser. No. 10/532,553, filed Apr. 22, 2005, abandoned, which claims priority to PCT International Application No. PCT/HU2003/000083, International Filing Date Oct. 21, 2003, the disclosures of which are hereby incorporated by reference.
The present invention generally relates to vehicle tires and, more specifically, to a non-pneumatic vehicle tire.
Tires currently used on vehicles are generally pneumatic tires. With such tires, internal air pressure is necessary to carry the load acting on the tires. Vehicle tires working with internal air pressure function well in practice, however, they do suffer from significant drawbacks. Such drawbacks include complex structural designs as well as safety issues in the event of a puncture during their use on public roads.
Airless or non-pneumatic tire designs exist in the prior art. For example, U.S. Pat. No. 1,610,238 to Benson discloses an airless vehicle tire in which arcuate or C-shaped springs are disposed radially around the tire. A ring-shaped wire spring running around the circumference of the tire is threaded through loops formed in the portions of the C-shaped springs situated in the crown portion of the tire. The ends of the C-shaped springs are bent into rings in the bead portions of the tire. A pair of ring-shaped springs, each of a diameter identical to that of the bead of the tire, are threaded one each through the rings on the ends of the C-shaped springs.
Similar radially-situated leaf springs are described in U.S. Pat. No. 1,113,036 to Mitchell. The C-shaped leaf springs in this solution, however, do not contain a loop on the crown portion of the tire.
According to U.S. Pat. No. 1,471,580 to Walton, springs prepared from wires of circular cross-section are formed in two symmetrically situated semi-circles and disposed radially within the tire so that a tunnel-like arrangement is formed. Both ends of each spring are provided with a fold-back in the form of a circle. Steel wires, which play the role of the bead-rings, are threaded through the circle-shaped fold-backs. In the circumferential direction, the radial springs are tied-up in pairs by a reinforcement in the crown portion of the tire. In this solution, the tire is pressurized to ensure the necessary loadability.
The disadvantage of the above prior art tires is that each is unsuitable for carrying loads over approximately 450 lbs. as the crown portions of the springs of each become flat, and, due to the large deformation, the springs fatigue and break. Another drawback of the vehicle tires of such construction is that they can be used only on vehicles with low traveling speeds (maximum 25-35 mph). In case of larger load or speed, the temperature of the vehicle tires significantly exceeds the acceptable temperature limit of 175-195° F. due to large spring deformations. As a consequence, the rubber material ages very quickly becoming thereby unsuitable for further use. A further disadvantage of the above prior art tires is the small side stability characteristic for their high profiles. This makes their safe operation in today's high-speed vehicles impossible.
The object of commonly assigned U.S. Pat. No. 6,374,887 to Subotics is a non-pneumatic vehicle tire reinforced by arch-shaped leaf springs, preferably made of a material such as steel, that are radially disposed within the tire. The tire features a crown portion containing the running surface and two side walls joined to the crown portion via shoulder portions. The two sidewalls end in beads which are clamped into a wheel rim. The crown portion, sidewalls and the beads are kept together by ribs made of an elastic material, which are supported by the arched leaf springs. The ends of the leaf springs are embedded flexibly into the beads, and the whole vehicle tire is mounted onto the wheel rim in a pre-stressed state.
A disadvantage of the non-pneumatic tire of the Subotics '887 patent, however, is that the strengthening ribs slip on the leaf springs during functioning, since the leaf springs are not built into the rubber body of the tire. The friction thus generated results in heat generation. A consequence of this is a significant heating-up of the tire during use. Furthermore, owing to the flexible embedding of the leaf spring ends into the beads, the tire beads also heat up significantly during operation due to the large deformation of the tires. In addition, under a high loading of the tires, the spring ends are pressed into the rubber material of the beads. As a result, the bead ends of the springs move away from each other and fold-like peak deformations are generated on the crown portion of the springs. These peak deformations result in breaking of the springs after only a short time of operation.
Accordingly, it is an object of the present invention to provide a non-pneumatic vehicle tire of high wear resistance, loadability, speed and side stability, eliminating, or at least reducing, the above disadvantages of known vehicle tires.
These and other objects and advantages will be apparent from the following specification.
The present invention is directed to a non-pneumatic tire for vehicles. The invention is based on the recognition that the disadvantages of known vehicle tires with springs originate mainly from the shape, material and arrangement of the leaf springs and from the mode of their joining with the rubber body of the tires.
The vehicle tire of the present invention features a body made of an elastic material, preferably rubber or polyurethane. The body has a crown portion containing the running surface and two sidewalls joined to the crown portion via shoulder portions and ending in beads. Radially placed curved springs are situated so as to be circumferentially-spaced in specified distances from each other and extend from one bead to the other. The tire's beads are secured within the flange of a rim of a conventional vehicle wheel by tension as the beads are stretched to get over the flange of the rim during installation of the tire onto the rim. According to the invention, the curved springs are embedded in the tire body at least along the crown portion.
In one embodiment of the non-pneumatic tire of the present invention, the shape of the curved springs in the angular range of 0≦t≦π from the one bead to the other can be described in an orthogonal coordinate system with axes X and Y by the equations x=a·cos t and y=b·sin t. This shape is semi-elliptical, where the semi-ellipse falls inside the range determined by ellipses:
In the ideal case:
The angle between the inwardly bent ends of the curved springs and the X axis of the orthogonal coordinate system, α, is preferably a minimum of approximately 8°, or preferably it is equal to the angle between the wheel rim portion fitting to the bead of the tire and the rotational axis of the wheel rim.
The curved springs on the crown portion are surrounded by two high-strength, low-stretch belt inserts with good dynamic properties. The belts are built completely into the rubber and are positioned radially outside of the springs.
A second embodiment of the non-pneumatic tire of the present invention, suitable for use on two-piece, dismountable wheel rims, features a construction identical to the first embodiment except the belts are omitted and the ends of the curved springs feature, in side-view, a horizontally-oriented C-shape, where, in the nest formed by the C-shape, a bead-ring is embedded into the rubber body of the beads. The circular bead-ring is preferably made of high-strength steel, circularly bent, stranded spring steel wires embedded into rubber or KEVLAR reinforced possibly by graphite or glass fibers.
In a third embodiment of the non-pneumatic tire of the present invention, a plurality of radially-extending and circumferentially-spaced compound-curve springs are at least partially embedded within the crown portion and the first and second sidewalls of the tire body, with each of the compound-curve springs having a first end terminating within the first bead of the tire body and a second end terminating within the second bead of the tire body. A circumferentially extending belt constructed of a high-strength and low stretch material positioned radially outside of the plurality of curved springs so as to surround them.
The springs are constructed of a composite material and each spring includes a first sidewall that is generally S-shaped and a second sidewall that is generally inverted S-shaped. More specifically, the sidewalls of each spring each includes upper and lower sidewall portions with the upper sidewall portions convex with respect to a radial plane of the tire and the lower sidewall portions concave with respect to the radial plane of the tire. Each spring also includes a top portion that is convex with respect to the rim of the vehicle wheel and end portions that are flat so as to generally lay along a horizontal axis. A circumferentially-extending snubber is made of an elastic material and is adapted to engage the rim of the vehicle wheel so as to be enclosed by the body of the tire.
It is preferable that the surfaces of the curved springs be treated with some material facilitating adhesion, preferably with the two-component CHEMOSIL solution, or a copper covering may be applied to the curved spring surfaces. Furthermore, it is preferable to cover the curved under the running surface with a rubber-coated strengthening material, such as steel belting or KEVLAR fabric.
The vehicle tire according to the invention can be used advantageously with every vehicle having tires including trucks, military vehicles, cars, etc.
The following detailed description of embodiments of the invention, taken in conjunction with the appended claims and accompanying drawings, provide a more complete understanding of the nature and scope of the invention.
Specific examples have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification.
A first embodiment of the vehicle tire of the present invention is illustrated in cross-section in
As illustrated in
As illustrated in
As illustrated in
Curved springs 2 preferably are covered by rubber at beads 1.4 and in the internal sides of sidewalls 1.3, and on the internal section 6 of crown portion 1.1. In order to ensure better heat conductivity, curved springs 2 may remain uncovered from below on the internal section 7 of shoulder portion 1.2. As will be described in greater detail below with respect to
A second embodiment of the vehicle tire according to the present invention is illustrated in cross-section and indicated in general at 1.5 in
Semi-ellipses 15, 16 and 17 intercepting axis X at point a, where 2a is the large axis of the ellipses and 2b, 2b′ and 2b″ are the small axes of the ellipses.
Thus the contour of curved spring 2 in the angular range of 0≦t≦π (0-180°) corresponds to an ellipse defined in an orthogonal coordinate system with axes X and Y by equations x=a·cos t and y=b·sin t and satisfying the following conditions:
In the ideal case:
In both the first and second embodiments of the vehicle tire of the present invention, as illustrated for the first embodiment in
The ends of curved springs 2 (and foot 10 of spring 2.1 in
The shock absorption of the vehicle tires of the first and second embodiments occurs due to the shape change of curved springs 2 or 2.1. Due to their semi-elliptical profiles, the shape change of the springs during load is distributed uniformly along the whole length of curved spring 2 or 2.1. In other words, no stress peaks occur which would lead to breaking. As a result, a dynamic life time similar or superior to that of conventional vehicle tires of radial or diagonal cord structure can be ensured.
The thin rubber layers covering bead portions 1.4 and 1.6 provide adhesion so as to hinder or prevent slippage of the beads 1.4 and 1.6 of the vehicle tires 1 and 1.5 on wheel rims 5 and 12, 13, respectively. The rubber layers do not play any role in the shock absorption of the vehicle tires.
As illustrated in
A third embodiment of the vehicle tire of the present invention is illustrated in
As indicated in general at 32 in
The beads of the tire 30.4 may optionally be provided with steel or composite bead rings, in the manner illustrated at 9 in
The material of the compound-curve springs 32 is preferably a thermoplastic matrix and glass fiber reinforcement composite, commonly known as fiber-reinforced plastic or fiberglass. The matrix is preferably poly-ethylene terephthalate (PET), also known as MYLAR, or polyester. Other thermoplastics, epoxy, vinyl ester or other thermosets may also be used as a matrix material. As an alternative to the glass fiber, ZYLON fiber or KEVLAR fiber may be used. As an alternative to the composite construction, the compound-curve springs 32 may be made of single-layer or multi-layer spring steel, graphite or KEVLAR with graphite or glass fiber reinforcements.
The compound-curve springs are preferably manufactured by pultrusion with subsequent thermoforming. A peel ply textured film is preferably applied to the spring mold before thermoforming the spring. During thermoforming, the thermoplastic matrix material flows into the voids, cracks and cavities of the peel ply to avoid a glossy surface and raise the surface roughness to promote bonding with materials later applied to the surface of the spring.
The tire is preferably produced by transfer molding. As illustrated in
As illustrated in
As with the first embodiment, the third embodiment of the tire of the present invention preferably includes a pair of belt inserts 33 embedded into the crown portion 30.1 of the tire above compound-curve springs 32. The portion of the crown above the belts, indicated at 38 in
The arrangement of the curved springs in the vehicle tire 30 of the third embodiment may also be described with reference to
Significant advantages of the vehicle tires according to the invention include:
Total safety in the event of punctures, since the vehicle tire does not have internal pressure, thus no air can escape which would deteriorate traveling properties.
The manufacturing process is well automatable and the production quality is reliable.
No monitoring/control of tire air pressure is necessary and there is no need for a spare tire.
The energy requirement of the manufacturing of the vehicle tire according to the invention is generally lower as compared to conventional tires. As a result, less environmental harm is caused.
Lower rolling resistance and superior fuel efficiency than a pneumatic tire.
While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.