FR3121072A1 - Structurally Supported Airless Crushable Envelope - Google Patents

Abstract

Structurally supported airless deformable casing (1) for a rolling object pushed or pulled at a speed of less than 25 km/h, or for an idler wheel of a vehicle whose maximum speed is less than 25 km/h, comprising a annular rolling strip (2) intended to roll on the ground, a plurality of spokes (3) extending transversely and radially inside the annular rolling strip (2). The annular rolling band (2) has circumferential and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa. The spokes (3) connecting the annular tread to the rim have radial and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa. Abstract Figure: Figure 1

Description

Structurally Supported Airless Crushable Envelope

The subject of the present invention is a deformable envelope without air with structural support, intended to equip a rolling object pushed or pulled such as a wheelbarrow, a hand truck, a bed on wheels, hospital or not, a piece of furniture on wheels, a launch for a boat, a trolley, etc. or an idler wheel, all with a maximum speed of less than 25 km/h.

This type of rolling object is either fitted with tires whose elasticity is ensured by the volume of air it contains (1937FR-0833640D), or fitted with a wheel whose outer casing is a thermoplastic tire or resin little or not deformable.

Tires have the disadvantage of puncturing and in many cases, the price of the tire and its replacement is more expensive than the object itself. This is particularly true for wheelbarrows which are used on construction sites where the ground contains metal objects such as nails, screws, iron wire capable of perforating tires.

Rigid wheels with metal or thermoplastic rims surrounded by a rigid thermoplastic tire are not suitable for regular use on ground comprising planks, steep edges a few centimeters thick such as are found on building sites to pass a hole, to lead to a somewhat elevated area, and so on.

A pneumatic wheelbarrow wheel deforms locally on the obstacle it crosses. It absorbs part of the energy of the impact with the obstacle and creates two contact surfaces, one vertical and one horizontal. These two surfaces each generate a contact force component, each normal to the surface. On the vertical surface, the force is in the direction of rotation of the wheel and tends to make it turn. On the horizontal surface, the component is vertical, it opposes the rotation but also tends to lift the axis of the wheelbarrow. With inertia, it is possible to pass the obstacle, especially since the pneumatic wheel releases the deformation energy by returning to its normal shape, helping to also lift the wheelbarrow axle.

For a wheel with a thermoplastic or resin tyre, the stiffness of the wheel is such that its deformation is almost nil and it almost instantaneously releases the impact energy perpendicular to the contact corner, through the entire rigid body of the the wheelbarrow in the arms of the user generating much more fatigue and in the long run musculoskeletal disorders. Thus, despite the advantage of not puncturing, wheels with a solid tire made of thermoplastic or other rigid materials have not been successful in the professional markets where the uses are nevertheless the most severe and where the advantage of a puncture-proof wheel is the most important.

• il peut s’agir de remplacer une roue pneumatique et de supprimer le problème de sa maintenance, quand l’usage exige l’utilisation d’une roue pneumatique. Par exemple les mises à l’eau pour bateau qui utilisent des roues pneumatiques qu’il faut regonfler ou réparer quand elles sont percées, qui roulent sur le sable ou des roues indéformables s’enfoncent et rendent la traction très difficile et ne sont donc pas utilisées.
• Il peut également s’agir de remplacer des roues avec un bandage plein qui doivent passer parfois rarement ou pas des obstacles, comme les roues de brancards, de chariot, les roues folles de fauteuil roulant.

These problems exist for many other vehicles pulled or pushed either by people or by animals. The problem is twofold:

• it may involve replacing a pneumatic wheel and eliminating the problem of its maintenance, when the use requires the use of a pneumatic wheel. For example boat launches which use pneumatic wheels which must be reinflated or repaired when they are punctured, which roll on the sand or non-deformable wheels sink and make traction very difficult and are therefore not used.
• It can also be a question of replacing wheels with a solid tire which must sometimes rarely or not pass obstacles, such as stretcher wheels, trolley wheels, wheelchair idler wheels.

A wheel having a geometry of revolution with respect to an axis of rotation, the geometry of the wheel is generally described in a meridian plane containing the axis of rotation of the wheel. For a given meridian plane, the radial, axial and circumferential directions designate respectively the directions perpendicular to the axis of rotation of the wheel, parallel to the axis of rotation of the wheel and perpendicular to the meridian plane. The circumferential direction is tangent to the circumference of the wheel. The axial direction is indifferently named axial or transverse. A plane perpendicular to the axis is called the circumferential plane.

The inventors have set themselves the objective of finding a puncture-proof device having the same or better obstacle-clearing capacity than a wheel fitted with a tire for pushed or pulled rolling objects, or for idle vehicle wheels, the all at a speed of less than 25 km/h.

• une bande annulaire de roulage destinée à rouler sur un sol,
• une pluralité de rayons s’étendant transversalement et radialement à l’intérieur de la bande annulaire de roulage,
• la bande annulaire de roulage ayant des modules élastiques circonférentiel et transverse au moins égaux à 1 MPa et au plus égaux à 100 MPa,
• les rayons ont des modules élastiques radial et transverse au moins égaux à 1 MPa et au plus égaux à 100 MPa.

This objective is achieved with a structurally supported airless deformable casing for a rolling object pushed or pulled at a speed of less than 25 km/h, or for an idler wheel of a vehicle whose maximum speed is less than 25 km/h , including:

• an annular rolling strip intended to roll on a ground,
• a plurality of spokes extending transversely and radially inside the annular rolling strip,
• the annular rolling strip having circumferential and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa,
• the spokes have radial and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa.

By deformable airless envelope, we mean a deformable object intended to be mounted on a rim made of rigid material, plastic, wood, metal, the whole of which forms a wheel for a rolling object or a vehicle. This wheel does not have a closed cavity intended to contain air or a gas in a hermetic or generally hermetic manner. It is elastically deformable, i.e. after use under the normal conditions of use of the rolling object or the vehicle, the deformable envelope without air with structural support returns to its initial shape. The airless deformable envelope is structurally supported, i.e. its elastic deformable function is ensured by a material structure, the annular rolling strip assembly and the plurality of spokes. The spokes are connected to the annular rolling strip by their most radially outer ends and connected to the rim by an attachment means which may be an inner annular strip, radially inner to the spokes. The elastic deformable function is not ensured by an airtight cavity containing air or a gas.

Conversely, tires contain air or a gas whose compression in an airtight chamber allows elastic operation.

This structurally supported airless crushable shroud is intended for use in which it does not transmit torque or drift stress to the object on which it is mounted. It can be mounted on a non-steering non-driving idler wheel of a motorized vehicle traveling at a speed of less than 25 km/h, such as the idler wheels of non-pushed or pulled electric wheelchairs, the sole function of which is to take up part of weight and stabilize the chair. Indeed the particularity of this deformable tire without air with structural support is to be particularly deformable and not to contain structural reinforcements usually contained in this type of object and in tires as a general rule. These structural reinforcements, metal cables or textiles of the aramid type, PET, etc., the length of which is at least equal to the axial width of the tire or of the deformable tire, have the function of taking up the torque and drift forces, which does not have of interest for pulled or pushed vehicles or idler wheels. They exist in tires, even for applications such as those targeted by the invention to simply take up the pressure forces. However, these textile or metal reinforcements inevitably stiffen the tires in question unnecessarily and make the deformation around the obstacle less efficient in terms of the “ease of passing obstacles” performance. These reinforcements ensure the absorption of the forces and in particular the load by traction of the spokes opposite the contact area. For optimal local deformation around the obstacle, the airless deformable casing with structural support must absorb the force by local crushing of the annular rolling strip and the spokes between the contact area and the rim. The structurally supported airless crushable envelope should therefore not contain long textile or metal reinforcements. Containing it would give the annular tread or the spokes a stiffness greater than 100 MPa. As a result, the structurally supported airless casing does not have the necessary structural strength to withstand centrifugation for a speed greater than 25 Km/h, or to pass torque or drift.

A wheel provided with a solid tire composed even of a material of low rigidity, less than 100 MPa, would not satisfy the object of the invention either, since a solid tire does not allow sufficient deformation around obstacles. In compression, a solid bandage has a much greater rigidity than a deformable envelope without air according to the invention.

This deformability of the invention is ensured on the one hand by the openwork structure of the spokes which represent less than 50% of the volume comprised between the annular tread and the rim of the wheel. This deformability is also ensured by the mechanical characteristics of the components undergoing deformation, of the deformable envelope without air with structural support, namely the annular rolling strip and the plurality of spokes connecting the annular rolling strip to the means for connect said spokes to the rim. The circumferential and transverse elastic moduli of the annular rolling strip are at least equal to 1 MPa and at most equal to 100 MPa, preferably at least equal to 5 MPa and at most equal to 15 MPa. In this range of materials from 1 to 100 MPa, the structurally supported airless deformable envelope is able to fulfill the function of carrying the load and passing obstacles and it deforms optimally on the obstacle. The textile or metal reinforcements of the tires take them out of this range, as do the tires filled with rigid materials.

By targeting a more restricted interval of 5 to 15 MPa, the advantage is that the deformable tire without air with structural support is then more resistant to wear during rolling, all the more so if it is made of rubbery materials.

Preferably, the annular rolling strip of the structurally supported airless deformable tire is made of a rubbery mixture, a rubber composition comprising at least one elastomer and a filler. To optimize the material, for resistance to abrasion or for specific uses, it is always possible to add short textile or metal fibers whose length is less than 25% of the axial width of the annular band. that do not excessively stiffen the components of the structurally supported airless crushable tire. The use of such fibers can generate different moduli according to the transverse and circumferential directions. It is essential to ensure good clearance of obstacles that these two modules are between 1 and 100 MPa, preferably between 5 and 15 MPa.

The same applies to the plurality of spokes connecting the annular rolling strip to the attachment means to the rim. They are preferably made of a rubbery mixture. They may contain short textile or metal fibers which may induce different radial and transverse moduli but which must be between 1 and 100 MPa and preferably between 5 and 15 MPa.

The thicknesses of the annular rolling strip and the spokes as well as their number will be determined by those skilled in the art according to the specifications of the object and its use.

The materials, in particular the rubber compounds, used in the deformable envelope without air with structural support according to the invention have stiffnesses estimated by their so-called "nominal" secant moduli at 10% elongation according to standard NF ISO 37 of December 2005 , between 1 MPa and 100 MPa, preferably between 5 and 15 MPa.

It is interesting that the deformable envelope is made of a single material. Thus it is possible to manufacture it by injection into a mould, a particularly effective process as regards the cohesion of the various components and very advantageous in terms of productivity.

By the deformable casing is meant all its various components, namely the annular rolling strip, the spokes and the means for connecting the plurality of spokes with a rim of a rolling object or of a vehicle whose maximum speed is less than 25 km/h. Among the means of connecting the spokes to the rim, an advantageous means is an annular strip radially inside the spokes and connected to them, capable of being mounted on the rim without risk of unseating.

It is preferred that the spokes be curved in a circumferential plane, perpendicular to the axis of rotation. Thus they all bend in the same direction during use and the contacts between these spokes do not oppose their deformations. By curves we mean that the spokes do not have a purely radial section in the various circumferential planes but have at least one point of inflection. They can be made up of two line segments making angles with the radial direction.

It is advantageous for the rays to make an average angle at least equal to 3° and at most equal to 10° with respect to the axial direction, called the transverse direction. Thus it is possible to distribute the rigidity given by each spoke over a certain circumferential length of the annular rolling strip. By creating this continuity of rigidity, rolling is also continuous, requires less energy and increases comfort of use. To measure the average angle of a ray with the axial direction, we will consider the angle made by the straight line connecting the two most axially exterior points, on either side of the circumferential plane passing through the center of the annular band of rolling, of the spoke considered at the level of its connection to the annular rolling strip and located on the neutral fiber of the spoke.

A preferred solution is that each ray make an average angle at least equal to 3° and at most equal to 10° with respect to the transverse direction and of opposite sign to the average angles made with respect to the transverse direction by the two rays being adjacent. By this alternation of the angles of the rays made with the transverse direction, the spaces between the two rays have a conical shape. A mold in two parts, each bearing a type of conical pattern whose larger bases will be extracted first from the molded object, will provide increased ease of release.

This solution has been developed especially for wheelbarrow wheels although this application is not exclusive. A preferred solution is therefore a structurally supported airless deformable casing intended to be mounted on a wheelbarrow with an external diameter between 300 mm and 450 mm, made of a single rubber compound whose modulus of elasticity is between 5 MPa and 15 MPa, which is perfectly suited for this purpose.

Preferably, this deformable airless casing with structural support for a wheelbarrow comprises an inner annular band intended to maintain said deformable casing on a wheelbarrow rim, the annular rolling band having a radial thickness of between 10 mm and 20 mm, the number of spokes connecting the annular rolling strip and the inner annular strip is between 25 and 35 and said spokes have a circumferential thickness of between 5 and 10 mm. Such a structure is optimal in terms of the volume of material used and therefore of mass.

A preferred solution is that this deformable envelope without air with structural support intended to be mounted on a wheelbarrow has, for a force applied on its axis of 70 kg, a variation in diameter of between 10 and 20 mm.

• figure 1 : vue perpendiculaire à l’axe de rotation d’une enveloppe déformable sans air à support structurel.
• Figure 2 : vue perpendiculaire à l’axe de rotation d’un quart d’enveloppe déformable sans air à support structurel illustrant la courbure des rayons 3 de ladite enveloppe déformable sans air à support structurel.
• Figure 3 : vue de 3 quarts de 3 rayons (3) consécutif de l’enveloppe déformable sans air à support structurel, faisant des angles a1, a2, a3 avec la direction transverse tels que a2 est de signe opposé à a1 et a3.

The characteristics of the invention are illustrated by the diagrammatic figures 1 to 3 and not shown to scale, with reference to a deformable envelope without air with structural support:

• FIG. 1: view perpendicular to the axis of rotation of a deformable envelope without air with structural support.
• Figure 2: view perpendicular to the axis of rotation of a quarter airless deformable envelope with structural support illustrating the curvature of the spokes 3 of said deformable airless envelope with structural support.
• Figure 3: view of 3 quarters of 3 consecutive rays (3) of the deformable envelope without air with structural support, forming angles a1, a2, a3 with the transverse direction such that a2 has the opposite sign to a1 and a3.

Figures 1 and 2 illustrate a structurally supported airless deformable casing 1 or part thereof, comprising an annular rolling strip 2, a plurality of spokes 3 extending transversely and radially inside the annular strip 2 rolling and means 5 for connecting the plurality of spokes 3 with a rim 4 of a rolling object not shown, these means 5 being here an inner annular band. There represents one of the simplest arrangements of the invention with purely radial rays.

There represents on a quarter of the deformable envelope without air with structural support, the curvature of the spokes 3 in the circumferential plane perpendicular to the axis of rotation. Thus the spokes are all forced to bend in the same direction, thus avoiding contact between two spokes opposing the flattening of the wheel during rolling.

There illustrates one of the possibilities of the invention where each ray 3 makes an angle a at least equal to 3° and at most 10° with respect to the transverse direction and of opposite sign to the angles made with respect to the transverse direction by the two rays being adjacent to it, the whole represented on 3 rays. This configuration makes it possible, due to the small space between two consecutive spokes 3 and the presence of a spoke 3 over a circumferential length of the annular rolling strip greater than the mere thickness of the spoke, to have good continuity of rigidity. from the deformable envelope without air to structural support all around the wheel giving a great comfort of use. Such an object also offers the advantage of being able to be produced in a mold closing by the relative displacement of two parts along the axis of rotation of the deformable envelope without air with structural support, each part bearing generally conical shapes which are very easy to unmold.

This invention was applied to a wheelbarrow wheel and compared with a pneumatic wheel inflated to 1.25 bar according to the manufacturer's instructions (between 1 and 1.5 bar) and a commercial rigid PET wheel. These solutions have the same diameter and the same width within 5%. Professional building users refuse to use the rigid wheel because obstacle clearance is too difficult with this solution. The pneumatic wheel remains the benchmark for users despite the risk of punctures.

The invention has a diameter of 400 mm in diameter. The annular rolling strip is 12 mm radially thick and 85 mm transversely wide. The means for hanging the structurally supported airless crushable envelope is an inner annular band 200 mm in diameter and 4 mm in radial thickness. 30 curved spokes in the circumferential plane connect the two annular bands. They are formed according to of two half-spokes forming an angle of 5° with the radial direction joining halfway between the two inner and rolling annular bands. They are of variable circumferential thicknesses of 6 to 8 mm. The extra thicknesses of 8 mm located at the junction of the spokes with the annular rolling strip and the inner annular strip and in their middle, bending zones of these spokes. This type of variation in thickness makes it possible to lighten the solution. The structurally supported airless crushable shell is force-fitted to a flat rim with outer flanges preventing transverse movement of the inner annular band relative to the rim. The rays have an angle (a1) of 8° with the transverse direction of opposite sign from one ray to the next as shown . The variation of the crushed radius for 70 kg of load on the axis, is 15 mm, identical to the tire of the commercial wheelbarrow.

The different solutions are tested on a wheelbarrow that has to cross a 40 mm high wooden step fixed to the ground. The arms of the wheelbarrow are equipped with idler wheels so as not to generate any resistance. The wheelbarrow is towed via a cable fitted with a dynamometer at a speed of 1 m per second, i.e. the speed of a man walking pushing such a load, i.e. 3.6 km/h. The wheelbarrow is loaded with a weight of 100Kg.

With the rigid wheel, the wheelbarrow does not cross the obstacle. With pneumatic tires or structurally supported airless crushable casing wheels, the wheelbarrow overcomes the obstacle. The effort required to overcome the obstacle is reduced by 10 to 20% for the wheel according to the invention compared to the wheel fitted with a tire.

The invention is therefore indeed a puncture-proof device having the same or better obstacle-clearing capacity than a wheel fitted with a tire for rolling objects pushed or pulled at a speed of less than 25 km/h. This solution is also interesting for the idler wheels of vehicles traveling at a speed of less than 25 km/h.

Claims (10)

Deformable airless casing with structural support (1) for a rolling object pushed or pulled at a speed of less than 25 km/h, or for an idler wheel of a vehicle whose maximum speed is less than 25 km/h, comprising:

• an annular rolling band (2) intended to roll on the ground,
• a plurality of spokes (3) extending transversely and radially inside the annular rolling strip (2),
• characterized in that the annular rolling band (2) has circumferential and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa,
• and in that the spokes (3) have radial and transverse elastic moduli at least equal to 1 MPa and at most equal to 100 MPa.

Deformable structurally supported airless envelope (1) according to claim 1 in which the annular rolling band (2) has circumferential and transverse elastic moduli at least equal to 5 MPa and at most equal to 15 MPa. Deformable structurally supported airless envelope (1) according to any one of claims 1 or 2 in which the spokes (3) have radial and transverse elastic moduli at least equal to 5 MPa and at most equal to 15 MPa. A structurally supported airless crushable envelope (1) according to any preceding claim wherein the crushable envelope is made of a single material. A structurally supported airless crushable envelope (1) according to any preceding claim wherein the spokes (3) are curved in a circumferential plane. Structurally supported airless deformable envelope (1) according to any one of the preceding claims, in which the rays make an average angle of at least equal to 3° and at most equal to 10° with respect to the transverse direction Structurally supported airless deformable envelope (1) according to any one of the preceding claims, in which each spoke (3) makes an average angle at least equal to 3° and at most equal to 10° with respect to the transverse direction and opposite sign to the angles made with respect to the transverse direction by the two rays adjacent to it. Structurally supported airless deformable cover (1) according to any one of the preceding claims intended to be mounted on a wheelbarrow, the external diameter of which is between 300 mm and 450 mm, made of a single rubbery mixture whose modulus of elasticity is between 5 MPa and 15 MPa, A structurally supported airless crushable tire (1) as claimed in any preceding claim for mounting on a wheelbarrow, comprising an inner annular band for securing said crushable tire to a wheelbarrow rim and wherein the rolling ring has a radial thickness of between 10 mm and 20 mm, the number of spokes connecting the rolling annular strip and the inner annular strip is between 25 and 35 and said spokes have a circumferential thickness of between 5 and 10 mm . . Deformable airless envelope with structural support (1) intended to be mounted on a wheelbarrow according to any one of the preceding claims such that for a force applied on its axis of 70 kg, its diameter variation is between 10 and 20 mm.