Patent Description:
The National Aeronautics and Space Administration (NASA) has developed surface vehicles to support long range lunar exploration, the development of a lunar outpost, and other planetary exploration. These vehicles are heavier and travel greater distances than the Lunar Roving Vehicle (LRV) developed for the Apollo program in the late <NUM>. Consequently, new tires will be required to support up to ten times the weight, and last for up to one hundred times the travel distance, as compared to those used on the Apollo LRV, thereby requiring operational characteristics similar to passenger vehicles used on earth. However, conventional rubber pneumatic tires cannot function acceptably in space.

For example, rubber properties vary significantly between the cold temperatures experienced in shadow (down to <NUM>) and the hot temperatures in sunlight (up to <NUM>). Further, rubber degrades when exposed to direct solar radiation, without atmospheric protection. Finally, an air-filled tire is not permissible for manned lunar vehicles because of the possibility of a flat tire. To overcome these limitations, a tire design has been developed for the Apollo LRV and was successfully used on Apollo missions <NUM>, <NUM>, and <NUM>. This non-pneumatic tire was woven from music wire, which was robust to lunar temperature variations and solar radiation, operated in vacuum, and did not require air for load support. This structure further functioned to contour to the lunar terrain, which facilitated traction and reduced vibration transfer to the Apollo LRV.

As stated above, because of the new weight and distance requirements for lunar vehicles, a tire with greater strength and durability was required. Further, it has been found that vehicles and tires on the moon may experience temperatures as low as <NUM>. One conventional wheel and non-pneumatic tire assembly has a variable diameter which, in addition to changing its diameter, may also change its width, thereby increasing the area of the tire that engages the lunar surface. Thus, this non-pneumatic tire may be adjusted to increase a vehicle's performance according to the terrain over which it is traveling. This tire/wheel may have arching members with first and second ends connecting a wheel hub. The arching members may be interlaced helical springs forming a partially compliant cage. The arching members may extend outwardly in an arc between the first and second ends. The arching members form a plurality of flexible hoops spaced circumferentially around the hub and extending radially outward from the hub. For example, the conventional cage may include thirty-eight equally spaced radially extending hoops that arch between axially outer rims of a hub. The hoops may be made of helical steel springs cut to a desired length and threaded through each adjacent spring. The conventional hub may be expanded/contracted axially for varying the diameter of the tire/wheel.

Thus, such a conventional non-pneumatic tire/wheel includes a plurality of helical springs. Each helical spring includes a first end portion, a second end portion, and an arching middle portion interconnecting the first end portion and the second end portion. Each helical spring is interwoven, or interlaced, with at least one other helical spring of the plurality thereby forming a woven toroidal structure extending about an entire circumference of the non-pneumatic tire/wheel. A subset of helical springs may be secured to a first annular rim of a wheel and/or a second annular rim of the wheel. A wheel with an annular rim at each axial side of the tire may secure the tire to the wheel. Thus, as compared to structures of conventional pneumatic tires, the woven/laced toroidal structure of interwoven helical springs may define a first ply for the non-pneumatic tire. A second ply may radially overlap the first ply. Such a second ply may comprise the same interwoven toroidal structure as the first ply. The conventional steel tire/wheel has now been found to experience temperatures as low as <NUM> on the moon. Steel becomes weak and brittle under such conditions. As a result, an improved non-pneumatic tire for use on the moon is desirable.

<CIT>, <CIT> and <CIT> describe an assembly in accordance with the preamble of claim <NUM>.

"Axial" and "axially" are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire.

"Gauge" refers generally to a measurement, and specifically to a thickness measurement.

"Harshness" means the amount of disturbance transmitted by a tire when it passes over minor, but continuous, road irregularities.

"Rim" means a support for a tire or a tire and tube assembly upon which the tire is secured.

Spring rate" means the stiffness of a tire or spring expressed as the slope of a load defection curve.

The invention relates to an assembly in accordance with claim <NUM>.

An assembly in accordance with the present invention has a wheel and a non-pneumatic tire. The nonpneumatic tire includes a plurality of helical springs. Each helical spring includes a first end portion, a second end portion, and an arching middle portion. Each helical spring is interlaced with at least one other helical spring thereby forming a laced toroidal structure extending about an entire circumference of the nonpneumatic tire. The toroidal structure supports an entire load placed on the nonpneumatic tire. The first end portions of the helical springs are directly secured to a first annular structure of the wheel and the second end portions of the helical springs are directly secured to a second annular structure of the wheel. The first end portion of each of the plurality of helical springs is oriented coaxially with the second end portion of each of the plurality of helical springs. The plurality of helical springs are constructed of a material that maintains strength and ductility down to <NUM>.

The structure, operation, and advantages of the present invention will become more apparent upon contemplation of the following description as viewed in conjunction with the accompanying drawings, wherein:.

A tire for use with the present invention and as described by <CIT> and <CIT> include an interlaced plurality of helical springs, preferably coiled wires which deform elastically under load with little energy loss. The tire defines a toroidal shaped structure for mounting to a wheel. The tire contours to a surface on which the tire engages to facilitate traction while mitigating vibration transmission to a corresponding vehicle. The helical springs support and/or distribute a load of a vehicle.

Under the weight of the vehicle, the tire may be driven, towed, or provide steering to the vehicle. The helical springs of the tire may passively contour to any terrain by flexing and moving with respect to each other. The interlaced structure of the helical springs provides stability to the tire and prevents the structure from collapsing as the tire rotates and engages variably terrain.

The helical springs of the tire may be resilient through a finite range of deformation, and thus a relatively rigid frame may be used to prevent excessive deformation. Radially oriented springs may be used to connect the tire to the wheel. These springs may be interlaced. Other springs may be incorporated with the tire at any bias angle, from radial to circumferential, with the purpose of distributing load. These other springs may be helical springs. Further, as one example, these other springs may extend circumferentially around the tire at a radially outer portion of the tire.

As one example, four basic steps may be utilized to manufacture one example tire: (i) twisting helical springs together to form a rectangular sheet with a length corresponding to the desired tire circumference; (ii) interlacing ends of the rectangular sheet of springs to form a mesh cylinder; (iii) collapsing one end of the mesh cylinder and attaching it to a rim of a wheel; and (iv) flipping the other end of the mesh cylinder inside out and attaching it to another axially opposite rim of the wheel.

The tire for use with the present invention may be utilized on Earth, the Moon, Mars, and/or any other planetary body, since its elements operate reliably in atmospheric and terrain conditions of these planets. The tire may be utilized on its own or incorporated as a partial or auxiliary load support/distribution system within another tire type. The tire, however, requires no air, requires no rubber, operates in difficult environments, and contours to all terrains.

The tire provides an improvement over the conventional wire mesh tire of the Apollo LRV. The tire provides higher load capacity, since wire size of the helical springs may be increased with relatively little functional alteration. The tire provides a longer cycle life, since wire stresses of the helical springs are more uniformly distributed throughout the structure. Further, the tire provides relatively low weight per unit of vehicle weight supported, since the interlaced helical spring network is fundamentally stronger than a crimped wire mesh. Additionally, the tire provides improved manufacturability, since the helical springs may be screwed, or interwoven, into one another, rather than woven together. Furthermore, helical springs are able to compress and elongate to accommodate manufacturing variations. Finally, the tire provides improved design versatility, since load distribution springs may be added to vary the tire strength in different tire locations and directions.

A tire for use with the present invention may thus be utilized where low vehicle energy consumption is required, where tire failure poses a critical threat, for traveling through rough terrain, where the vehicle is exposed to extreme high and low temperatures or high levels of radiation.

As shown in <FIG>, an example assembly <NUM> in accordance with the present invention includes a wheel <NUM> and a tire <NUM>. The wheel <NUM> has an annular rim <NUM> at each axial side for securing the tire <NUM> to the wheel. Each rim is fixed <NUM> relative to the other rim <NUM>. Each rim <NUM> may include a plurality of socket holes <NUM> for aligning the tire <NUM> with the rim. Any other suitable means may be used for securing the tire <NUM> to the rim <NUM>.

The tire <NUM> includes a plurality of helical springs <NUM> extending radially away from the wheel <NUM> in an arching configuration and radially back toward the wheel. Each end <NUM> of each spring <NUM> is secured to wheel at a corresponding rim <NUM> of the wheel. Each spring <NUM> has a middle portion interconnecting the ends <NUM>. Each end <NUM> may be secured at an axial orientation or at an angled orientation, with the spring <NUM> extending outward from one rim <NUM>, then away from the wheel <NUM>, then back over itself, then inward, and finally toward the other rim <NUM>. Each end <NUM> of each spring may thereby be oriented coaxially (or at an angle) with the other end <NUM> of the same spring.

Further, is spring <NUM> be interlaced with adjacent springs <NUM> enabling load sharing between springs. Each spring <NUM> is interlaced, or interwoven, with an adjacent spring <NUM> on a first side of the spring and further being interlaced with an adjacent spring <NUM> on a second opposite side of the spring. Thus, the springs <NUM> extend radially and axially and form a laced toroidal structure extending about an entire circumference of the tire <NUM> (<FIG>).

The helical springs <NUM> may be any suitable length, gauge, and pitch. The helical springs <NUM> may vary in coil diameter (i.e., barrel springs may be used) to create continuity in the mesh through the range of radial positions in the tire. The helical springs <NUM> may be further structured as two or more plies, one or more radially inner plies being radially overlapped by one or more radially outer plies.

The purely metallic, conventional non-pneumatic spring tire <NUM> described above has been developed for space applications. The structure is a series of interwoven springs as seen in <FIG>. This structure was well suited to space applications where rubber is not permitted due to temperature variations (<NUM> to <NUM>). In addition, the spring tire <NUM> may achieve excellent traction where soil composition may be soft sand such as the Moon.

It has been found that permanently shadowed craters on the Moon may feature some of the lowest temperatures in the solar system - down to <NUM>. Water ice may be stable at these temperatures, and it is believed that some of these craters harbor significant ice deposits. Consequently, according to the present invention, the spring tire <NUM> is constructed of a material that retains its strength and ductility at temperatures as low as <NUM>.

A conventional spring tire for the Moon has been constructed of materials which can survive and remain stable between <NUM> and <NUM> based on the then knowledge of the lunar temperature. As stated above, lunar temperatures may be as cold as <NUM>. Therefore, a new spring tire needs to be considered for lunar exploration to the permanent shadowed region of the lunar surface. Thus, a spring tire <NUM> with metallic alloys that would survive temperatures ranging from <NUM> to <NUM> is desirable. Ideally, such metallic alloys would function at extremely low cryogenic temperatures as low as <NUM> and even down to <NUM>.

One suitable material is 304ELC stainless steel and/or <NUM> Low-C stainless steel. Such a material maintains strength and ductility down to <NUM>.

Another suitable material is <NUM>-T4 aluminum, <NUM>-T6 aluminum, <NUM>-T87 aluminum, <NUM>-H38 aluminum, and/or <NUM>-H38 aluminum. Such a material maintains strength and ductility down to <NUM>.

Still another suitable material is nickel-based monel, TD Nickel, nickel-based Hastlelloy B, nickel-based Inconel X, nickel-based Inconel <NUM>, and/or nickel-based Rene <NUM>. Such a material maintains strength and ductility down to <NUM>.

Yet another suitable material is 5Al-<NUM>. 5Sn-Ti ELI titanium and/or Ti45A [AMS <NUM>] titanium. Such a material maintains strength and ductility down to <NUM>.

Still another suitable material is nickel-based Inconel <NUM>. Such a material maintains strength and ductility down to <NUM>.

Claim 1:
An assembly comprising a wheel (<NUM>) and a non-pneumatic tire (<NUM>), the non-pneumatic tire (<NUM>) comprising a plurality of helical springs (<NUM>), each helical spring (<NUM>) comprising a first end portion, a second end portion, and an arching middle portion, wherein each helical spring (<NUM>) is interlaced with at least one other helical spring (<NUM>) thereby forming a laced toroidal structure extending about an entire circumference of the non-pneumatic tire (<NUM>), and wherein the first end portions of a plurality of helical springs (<NUM>) are directly secured to a first annular structure of the wheel (<NUM>) and the second end portions of the plurality of helical springs (<NUM>) are directly secured to a second annular structure of the wheel (<NUM>), the first end portion of each of the plurality of helical springs (<NUM>) being oriented coaxially with the second end portion of each of the plurality of helical springs (<NUM>), characterized in that the plurality of helical springs (<NUM>) are constructed of 304ELC stainless steel, <NUM> Low-C stainless steel, <NUM>-T4 aluminum, <NUM>-T6 aluminum, <NUM>-T87 aluminum, <NUM>-H38 aluminum, <NUM>-H38 aluminum, nickel-based Monel, TD Nickel, nickel-based Hastlelloy B, nickel-based Inconel X, nickel-based Inconel <NUM>, nickel-based Rene <NUM>, 5Al-<NUM>.5Sn-Ti ELI titanium, Ti45A [AMS <NUM>] titanium or multiphase Co-35Ni-20Mo-10Cr alloy MP35N.