DEFORMABLE WHEEL WITH NON-PNEUMATIC RIMMING RIMMING AND METAL BENDING BAND FOR MOON AND MARS CONDITIONS

Description

Background of the invention

[0001] The present invention relates to a deformable wheel with a non-pneumatic load support. More particularly, the invention relates to a wheel that supports a load with its structural components and that has performance capabilities suitable for equipping a vehicle intended to operate in extreme conditions such as those encountered on the Moon and Mars.

[0002] Pneumatic tires possess load-bearing capacity, road shock absorption, and power transmission capabilities (acceleration, braking, and changes of direction) that are particularly well-suited to many vehicles, including bicycles, motorcycles, cars, and trucks. The shock-absorbing properties of pneumatic tires are also useful in other applications, such as carts transporting medical equipment or sensitive electronics.

[0003] Alternatives to pneumatic tires exist. These include solid tires and pneumatic tires. However, these alternatives do not offer the same performance advantages as pneumatic tires. In particular, solid tires rely on compression of the part in contact with the ground to support the load. This type of tire can be heavy and rigid and lacks the shock absorption capacity of pneumatic tires. When made more elastic, conventional non-pneumatic wheels do not have the load-bearing capacity or durability of pneumatic tires.

[0004] To remedy these drawbacks, US publication 7,418,988 proposes a structurally supported tire that includes an outer annular band and a plurality of spokes extending transversely and radially inward from the annular band to the wheel hub and intended to transmit in tension the load forces between the annular band and the hub.

[0005] The structurally supported wheel according to this invention does not have a cavity for containing pressurized air and therefore does not require a seal with the wheel rim to maintain internal air pressure. This structurally supported wheel thus does not require a tire in the conventional sense.

[0006] The spokes of this wheel act under tension to transmit load forces between the wheel and the rim, thus enabling it to support the mass of a vehicle. These support forces are generated by the tension of the spokes that are not connected to the portion of the rim in contact with the ground. The spokes also transmit the forces required for acceleration, braking, and cornering.

[0007] Whatever prior art alternatives exist for manufacturing non-pneumatic wheels, they generally do not provide complete satisfaction, especially when intended for use in extreme conditions such as those encountered on the Moon and Mars. Indeed, in such conditions, it is necessary for the wheel to deform significantly upon encountering an obstacle while generating a low and uniform contact pressure to allow the vehicle to remain mobile on soft ground like that found on the Moon and Mars.

[0008] Patent application EP22192685, filed on August 29, 2022, by the Applicant, describes a wheel that meets these needs, notably due to the presence of a laminated annular band comprising a plurality of concentric rings assembled with interposed layers, each composed of a material whose Young's modulus is 600,000 to 1,000 times lower than that of the rings, for example, an elastomeric material. Under an externally applied load, the portion of the laminated band in contact with the ground deforms, not into an essentially circular shape, but into a shape conforming to the ground surface while maintaining an essentially constant ring length. The wheel described in this patent application thus generates a low and uniform contact pressure on the ground.In this way, the vehicle equipped with such wheels can remain mobile (i.e., it does not get stuck in the sand) even on soft ground (like sand) such as that found on the Moon and on Mars.

[0009] The elastomer-based structure of the interlayers of the laminated tread of such a wheel has a minimum operating temperature between -140°C and -150°C, allowing the wheel to operate on most missions around the lunar south pole and at all latitudes on Mars (where the absolute minimum temperature is -120°C). However, this limitation can pose problems if the vehicle equipped with such wheels must travel to permanently shadowed regions (PSRs), such as the lunar poles, where temperatures are consistently between -220°C and -240°C. CN 107 856 478 describes a tread structure that includes a spring assembly embedded in a rubber ring. Object and summary of the invention

[0010] The main purpose of the present invention is therefore to overcome such drawbacks by proposing a deformable wheel structure with non-pneumatic load support that can be fitted to vehicles intended to travel in permanently shaded regions of the Moon where temperatures are constantly in the range of -220°C to -240°C.

[0011] According to the invention, this goal is achieved by means of a deformable wheel with non-pneumatic load support according to claim 1.

[0012] The wheel according to the invention is remarkable in that the tread is an all-metal flexible band that can remain flexible at temperatures as low as -250°C, typically found in permanently shadowed regions of the Moon. In particular, this flexural strength of the tread is achieved without the need to heat the tread.

[0013] Preferably, the corrugations of the tread core have a triangular cross-section.

[0014] Preferably, the tread springs are also positioned in several annular rows.

[0015] The radial reinforcements connecting the tread to the hub may advantageously include springs. Alternatively, the radial reinforcements may include wire cables.

[0016] As for the tread flange, it can be made of metal or composite material. Brief description of the drawings

[0017] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures: there figure 1is a schematic, front view of a wheel according to one embodiment of the invention; the figure 2 is a perspective and cross-sectional view of the wheel of the figure 1 ; there figure 3 is a perspective view of the wheel's flex band figure 1 ; and the figure 4 is a magnifying glass of the figure 3 showing the assembly of a bending band spring. Detailed description of implementation methods

[0018] The invention relates to a deformable wheel with a non-pneumatic load support as shown in the figure 1 which is suitable for equipping a vehicle intended to operate in extreme conditions such as those encountered on the Moon and Mars.

[0019] Wheel 2 shown on the figure 1comprises mainly a hub 4, an annular tread 6 having an outer surface intended to be in contact with the ground by being able to deform under an externally applied load to conform to the ground surface, and a plurality of radial reinforcements (here metal cables 8) radially connecting the hub to the tread.

[0020] According to the invention, the tread 6 is a flexing tread which includes a metallic core 10 provided with a plurality of undulations 12 sandwiched between a ferrule 14 and a plurality of circumferential springs 16 allowing the tread to deform in bending.

[0021] More specifically, as shown in 2 and 3, the undulations 12 of the tread's core 10 are formed from metal sheets that are V-bent in the longitudinal direction (i.e., parallel to the longitudinal axis of rotation XX of the wheel 2).

[0022] Thus, the undulations 12 of the web 10 of the tread each have a cross-section (i.e., according to a plane of cut transverse to the wheel) of triangular shape.

[0023] Note that the V-shaped point of the metal sheets that form the undulations 12 is turned towards the inside of the wheel (i.e. towards its axis of rotation XX) and flares outwards from the outside of the wheel.

[0024] It should also be noted that each undulation 12 of the tread core is symmetrical with respect to a plane P radial to the wheel (and passing through the V-shaped tip of the undulation).

[0025] It should also be noted that the metal sheets which make up the corrugations advantageously have 18 holes which are distributed along their entire length in order to lighten the weight of the wheel.

[0026] Furthermore, the 12 corrugations of the tread core can be made, for example, of stainless steel or titanium.

[0027] The ferrule 14 of the tread 6 of the wheel according to the invention is made of metal (for example, spring stainless steel or TA6V type titanium) or of composite material (for example, glass fibers or carbon fibers).

[0028] When the tread flange 14 is made of metal, the corrugations 12 of the core can be welded, brazed or riveted to it.

[0029] Thus, in the case of a ferrule 14 made of composite materials, the corrugations 12 are preferably fixed using metal rivets. In this case, the corrugations 12 may include a number of grooves on the top and bottom, not shown in the figures, so as to provide flexibility along the direction of the wheel's axis of rotation, allowing for differential expansion between the ferrule 14 and the corrugations 12 without introducing high stresses that could compromise the integrity of the structure.

[0030] Finally, the tread 6 of the wheel according to the invention includes a plurality of circumferential springs 16 allowing the tread to deform in bending.

[0031] Preferably, the tread springs 16 are positioned in several parallel rows extending in a circumferential direction around the wheel.

[0032] Thus, on the embodiment shown on the figures 2 And 3 , the 16 springs are distributed in seventeen rows parallel to each other.

[0033] There figure 4 illustrates an example of assembling a spring 16 onto a corrugation 12 of the tread core. In this example, the V-shaped tip of the corrugation 12 includes a plurality of perforations 20 through which the springs 16 pass, thus enabling the springs to be fixed to the corrugations.

[0034] As previously stated, in the implementation method of figures 1 to 4 , the radial reinforcements radially linking the wheel hub 4 to the tread 6 are composed of metal cables 8.

[0035] More specifically, in this embodiment, the cables 8 can be fixed, at an inner end, to one of the two lateral edges 4a of the hub 4, and at an opposite outer end, directly to the ferrule 14 of the tread.

[0036] Furthermore, by way of example, each cable 8 can be composed of an assembly of metallic wires (for example, steel) arranged in strands, themselves wound around a metallic core. Preferably, the cables 8 exhibit an asymmetry of stiffness, with a tensile mechanical stiffness Kt that is significantly greater than their compressive mechanical stiffness Kc.

[0037] Similarly, the number, distribution, and inclination of the cables 8 may vary. Reference may be made to patent application EP22192685 filed on August 29, 2022, by the Applicant, which describes a particular cable architecture.

[0038] It should be noted that the respective inner end of the cables 8 is advantageously fixed to the hub 4 by means of leaf springs or U-shaped folded leaves (not shown in the figures) allowing the radial stiffness of the cables to be modulated.

[0039] It should also be noted that instead of metal cables, the radial reinforcements connecting the wheel hub 4 to the tread 6 can be composed of springs (this embodiment is not shown in the figures).

[0040] Thanks to this wheel composition, the part of the tread that is in contact with the ground deforms under an externally applied load but in a shape that conforms to the ground surface.

Claims

1. A deformable wheel (2) with non-pneumatic load-bearing support intended to equip a vehicle for traveling in extreme conditions such as those encountered on the moon and Mars, comprising: a hub (4), an annular tread band (6) positioned around the hub and having an outer surface that is intended to be in contact with the ground being able to deform under an applied load from the outside in order to mold to the surface of the ground, and a plurality of radial reinforcements (8) connecting the tread band to the hub, the tread band being a flexion band comprising a metallic core (10) with a plurality of corrugations (12) sandwiched between an annular band (14) and a plurality of circumferential springs (16) allowing the tread band to deform in flexion, characterized in that the corrugations (12) of the core of the tread band are formed from V-folded metal sheets.

2. The wheel according to claim 1, wherein the corrugations (12) of the core of the tread band have a triangular cross-section shape.

3. The wheel according to one of claims 1 and 2, wherein the springs (16) of the tread band are positioned according to several annular rows.

4. The wheel according to any one of claims 1 to 3, wherein the radial reinforcements connecting the tread band to the hub comprise springs.

5. The wheel according to any one of claims 1 to 3, wherein the radial reinforcements connecting the tread band to the hub comprise metallic cables (8).

6. The wheel according to any one of claims 1 to 5, wherein the annular band (14) is realized of metal or composite material.