IGNITION WHEEL WITH METAL BENDING BAND FOR CONDITIONS ON THE MOON AND MARS

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. Even when made more elastic, conventional non-pneumatic wheels do not have the same load-bearing capacity or durability as 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 wheel described in this patent application also includes discs attached to the hub that project radially outwards to form stops that limit the movement of the wheel's tread. Indeed, depending on the size of the obstacles the wheel encounters, the inner surface of the laminated tread can come into contact with these discs mounted on the hub, thus limiting the deformations experienced by the laminated tread.

[0010] Furthermore, depending on the use of the vehicle, it may be advantageous to be able to drive over short distances and at reduced speed while carrying loads such that the inner surface of the laminated strip can come into permanent contact with the discs carried by the hub, even in the absence of an obstacle.

[0011] However, in these situations, due to the significant differences in tangential speed between the tread and the stop discs, the tread slips on the discs, which can damage the stops and severely alter the inner surface of the tread. The integrity of the wheel is therefore compromised.

[0012] The disclosure of document US 2019 / 217665-A1 is also relevant to understanding the invention. Object and summary of the invention

[0013] The main purpose of the present invention is therefore to overcome such drawbacks by proposing a deformable wheel structure with non-pneumatic load support which has a device to prevent any alteration of the tread when it is brought to a stop.

[0014] According to the invention, this goal is achieved by means of a deformable wheel with a non-pneumatic load support intended to equip a vehicle for driving in extreme conditions such as those encountered on the moon and on Mars, comprising: a hub carrying at least one thrust disc which protrudes radially outwards, an annular tread positioned around the hub and having an outer surface which is intended to be in contact with the ground by being able to deform under a load applied from the outside to conform to the ground surface, and an inner surface which is able to bear against the thrust disc in order to limit the deformations of the tread in radial directions, and a plurality of radial reinforcements connecting the tread to the hub, and wherein, according to the invention, the thrust disc is mounted to rotate freely on the hub so as to be able to be set in rotation when the inner surface of the tread comes to bear against the thrust disc.

[0015] The wheel according to the invention is remarkable in that the thrust disc is mounted to rotate freely on the hub, allowing it to "roll" when the tread comes into contact with it, regardless of speed differences. This system is thus similar to a ball bearing type device that only engages when the tread makes contact with the thrust. Because of this rolling capability of the thrust disc, the risk of damage to the tread, and therefore to the wheel, is significantly reduced.

[0016] Preferably, the thrust disc is mounted on an external surface of the hub via a roller bearing.

[0017] In this case, the roller bearing may comprise a plurality of cylindrical rollers mounted between the outer surface of the hub and an inner annular band of the thrust disc.

[0018] The thrust disc may include an outer annular band which is mounted around the inner band by means of a plurality of spring links.

[0019] In this case, the spring links can each be formed by a deformable ring.

[0020] The deformable ring of the spring links is advantageously composed of windings of a stainless steel strip.

[0021] Preferably, each spring link further includes a rigid stop ring mounted inside the ring.

[0022] The cylindrical rollers are advantageously evenly distributed on the outer surface of the hub around an axis of rotation of the wheel.

[0023] Preferably, the outer band of the stop disc is covered with an outer leather protection.

[0024] The hub can carry two thrust discs spaced apart along a wheel rotation axis.

[0025] The tread can be a metallic shear strip comprising a metallic core with corrugations sandwiched between a ferrule and a plurality of circumferential springs allowing the tread to deform in bending. Brief description of the drawings

[0026] 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 1 is 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 ; and the figure 3is a cross-sectional view of the wheel of the figure 1 . Detailed description of implementation methods

[0027] 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.

[0028] Wheel 2 shown on the figure 1 comprises 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.

[0029] In this embodiment, the tread 6 is a flexing tread which includes a metallic core 10 having a plurality of undulations 12 sandwiched between a ferrule 14 and a plurality of circumferential springs 16 allowing the tread to deform in bending.

[0030] 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).

[0031] 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.

[0032] 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).

[0033] 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.

[0034] The ferrule 14 of the tread 6 of the wheel according to this embodiment is made of metal or composite material (for example, glass fibers or carbon fibers).

[0035] Finally, the tread 6 of the wheel according to this embodiment includes a plurality of circumferential springs 16 allowing the tread to deform in bending.

[0036] As previously stated, in this embodiment, the radial reinforcements radially connecting the wheel hub 4 to the tread 6 are composed of metal cables 8.

[0037] 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).

[0038] Similarly, in another embodiment (not shown in the figures), the tread is a laminated annular strip comprising a plurality of concentric rings which are assembled with interposition of interposition layers each composed of a material whose Young's modulus is 600,000 to 1,000 times lower than that of the rings.

[0039] The ferrules of such a laminated strip can be made of metal or composite material, while the interposition layers can be composed of a hyperelastic elastomer having a glass transition temperature below 120°C.

[0040] Reference can be made to patent application EP22192685 filed on August 29, 2022 by the Applicant, which describes such a laminated tread wheel architecture.

[0041] Regardless of the embodiment, the wheel hub 4 carries at least one thrust disc 20 which protrudes radially outwards from the wheel.

[0042] When the ground surface on which the wheel 2 rolls presents a significant obstacle (for example, a rock), the portion of the tread 6 in contact with the ground deforms to conform to the obstacle's profile. In such a situation, depending on the size of the obstacle, the inner surface of the tread may come into contact with the outer diameter of the thrust disc 20 mounted on the hub 4 in order to limit the deformation of the tread. A similar situation can occur during low-speed rolling under heavy load.

[0043] According to the invention, the thrust disc 20 is mounted to rotate freely on the hub 4 so that it can be rotated around the axis XX of the wheel when the inner surface of the tread 6 comes into contact with the thrust disc.

[0044] More specifically, in the implementation of figures 1 to 3, the thrust disc 20 is mounted on an outer surface of the hub 4 via a roller bearing 22.

[0045] This roller bearing 22 preferably comprises a plurality of cylindrical rollers 24 which are mounted between the outer surface of the hub 4 and an inner annular band 26 of the thrust disc. The cylindrical rollers 24 are evenly distributed around the axis of rotation XX of the wheel.

[0046] Thus, when the inner surface of the tread 6 comes into contact with the outer diameter of the thrust disc 20 (particularly when the wheel rolls over a large obstacle), the latter can roll around the hub despite the differences in rotational speeds of the hub and the tread.

[0047] According to an advantageous arrangement, the stop disc 20 also includes an outer annular band 28 which is mounted around the inner band 26 via a plurality of spring links 30.

[0048] In the method of implementation of figures 1 to 3 The spring links are each formed by a deformable ring 30, advantageously composed of several windings of a stainless steel strip (for example, twelve windings of a strip 0.15 mm thick). Alternatively, these rings can be made of fiberglass-resin composite materials.

[0049] It should be noted that the deformable rings 30 are preferably regularly distributed all around the axis of rotation XX of the wheel.

[0050] According to another advantageous arrangement, each spring link further includes a ring 32 forming a rigid stop which is mounted inside the ring 30.

[0051] This ring 32 can be fixed to the inner edge 26 of the thrust disc or to the outer edge 28 of the thrust disc. It prevents the deformable rings 30 from deforming excessively in the event of significant tread deformation.

[0052] According to yet another advantageous arrangement, the outer band 28 of the stop disc is covered with an outer protection 34 for example of leather.

[0053] In another embodiment not shown, the wheel hub carries two thrust discs spaced apart along the axis of rotation XX of the wheel.

Claims

1. A deformable wheel (2) with non-pneumatic load bearing intended to equip a vehicle for rolling under extreme conditions such as those encountered on the Moon and on Mars, comprising: a hub (4) bearing at least one stop disc (20) which projects radially outwards: an annular tread layer (6) positioned around the hub and having an outer surface which is intended to be in contact with the ground, being able to deform under an externally applied load in order to match the surface of the ground, and an inner surface which is able to come to bear against the stop disc in order to limit the deformation of the tread layer in the radial direction, and a plurality of radial reinforcements (8) linking the tread layer to the hub, characterised in that the stop disc (20) is rotatably mounted on the hub in such a way as to be able to be rotated when the inner surface of the tread layer comes to bear against the stop disc.

2. The wheel according to claim 1, wherein the stop disc (20) is mounted on an outer surface of the hub (4) by means of a roller bearing (22).

3. The wheel according to claim 2, wherein the roller bearing (22) comprises a plurality of cylindrical rollers (24) mounted between the outer surface of the hub and an inner annular strip (26) of the stop disc (20).

4. The wheel according to claim 3, wherein the stop disc (20) comprises an outer annular strip (28) which is mounted around the inner strip (26) by means of a plurality of spring connections (30).

5. The wheel according to claim 4, wherein the spring connections are each formed by a deformable ring (30).

6. The wheel according to claim 5, wherein the deformable ring (30) of the spring connections is composed of windings of a stainless-steel strip.

7. The wheel according to one of claims 5 and 6, wherein each spring connection further comprises a bushing (32) forming a rigid stop mounted inside the ring (30).

8. The wheel according to any one of claims 3 to 7, wherein the cylindrical rollers (24) are regularly distributed on the outer surface of the hub (4) around an axis of rotation (X-X) of the wheel.

9. The wheel according to any one of claims 3 to 8, wherein the outer strip (28) of the stop disc (20) is covered with an outer protection (34) made of leather.

10. The wheel according to any one of claims 1 to 9, wherein the hub (4) bears two stop discs spaced apart from one another along an axis of rotation (X-X) of the wheel.

11. The wheel according to any one of claims 1 to 10, wherein the tread layer (6) is a metal shear strip comprising a metal core (10) provided with corrugations (12) sandwiched between a ferrule (14) and a plurality of circumferential springs (16) giving the tread layer the ability to deform in flexion.