Method and device for absorbing the shock experienced by a payload when landing it

Abstract

A shock-absorbing assembly 125 for a payload 110 transported on a dropping platform, comprises a shock-absorbing element 135, which can be viscoelastic, which extends along a plane and absorbs a shock

Description

TITLE: Method and device for absorbing the shock experienced by a payload when landing it Technical field The invention relates to the protection of a payload such as vehicles or machines, on wheels or crawlers, during the transport thereof, but especially during the dropping thereof, packaged in bundles, from an aircraft. Prior art For many reasons, it may be necessary to drop payloads from aircraft, for example vehicles. To protect these pay loads when landing on the ground, shockabsorbing devices must be provided. In particular, there are shock-absorbing systems based on honeycomb cardboard. The establishment of such a system for absorbing the shock of a vehicle to be dropped consists in assembling “stacks” of honeycomb cardboard sized so as to ensure a desired crushing rate, and then arranging these cardboard stacks on the dropping platform according to a specific plan described in user documentation which differs depending on the payload type. After glueing the cardboard stacks and allowing them to dry, it is necessary to sling the payload to be dropped, lift it, place the preequipped platform under the vehicle, then lower the payload onto the cardboard stacks before securing it to the platform. During the impact, upon landing, it is the crushing of the cardboard, by vertical buckling, which absorbs the kinetic energy and which absorbs the shock. Once on the ground, it is necessary to remove the restraints and then the cardboard blocks to release the vehicle. Although this solution is effective, it has many drawbacks. In particular, the establishment of such a system requires several hours of preparation and drying and the arrangement of the cardboard stacks varies according to the payload to be loaded, which requires a careful examination of the user documentation. Furthermore, this solution requires considerable handling means such as hoists or gantry cranes. Moreover, it is rare, upon a landing impact, that the platform lands at a speed perfectly perpendicular to the ground. Indeed, the platform generally lands with a low horizontal speed which often requires oversizing the cardboard stacks, with the risk of them not crushing enough and the payload not touching the platform after landing, which complicates the recovery. Finally, the recovery of the vehicle is often tedious and time-consuming, in particular because the cardboard placed under the vehicle must be pulled out before it could be extracted from the platform. There are also solutions based on a pneumatic system secured to an airdropping platform. This system comprises lifting cushions conferring two positions on the system, an uninflated position allowing rolling a vehicle onto the platform in order to position its wheels on this system, and an inflated position in which the vehicle is raised at all four of its wheels. Furthermore, the lifting cushions act as shock absorbers upon an impact by deformation. Moreover, cylinders are used to dampen the oscillations of the vehicle and control movement thereof relative to the platform. Such a system is particularly described in patent application WO 2012 / 003285. These systems also have drawbacks. In particular, they pose a risk of damage to the vehicle suspension. Disclosure of the invention The aim of the invention is to provide a shock-absorbing system for a payload, which is efficient, simple to install and remove, reusable and which protects the various elements of the payload, particularly the suspensions when the payload is a vehicle. According to one aspect, the object of the invention is a shock-absorbing assembly for a payload transported on a dropping platform, said assembly comprising - a shock-absorbing element extending along a plane and configured to absorb a shock along an axis essentially perpendicular to said plane and - a lifting device, separate from the shock-absorbing element, comprising an inflatable lifting cushion provided with a filling, closing and emptying element, the lifting device being configured to bear on said payload and on said dropping platform, along an axis perpendicular to the plane and through said shock-absorbing element. The shock-absorbing assembly according to the invention is easy to store, handle, implement and remove. It protects a payload against vertical impacts and also against vertical impacts with a horizontal component. The shock-absorbing assembly according to the invention allows absorbing the shock of a payload such as a vehicle upon an impact, in particular an impact upon landing following a drop, for example by an aircraft. It makes simple and cost-effective the deployment and retrieval, for example with the help of one single operator and a simple compressed air compressor (for the establishment). It takes up little space, requires no special handling means and can be reused. According to one feature, the lifting device further comprises - a guiding element provided with a cylindrical cavity extending along a longitudinal axis perpendicular to said plane and having an end at least partially closed along a plane parallel to said plane and - an element sliding in the cylindrical cavity along a longitudinal axis of the cylindrical cavity and extending outside the cylindrical cavity, opposite said end, said inflatable lifting cushion being arranged in the cylindrical cavity, between said end and the sliding element, and one of the guiding element and of the sliding element being configured to bear on said payload and the other of the guiding element and of the sliding element being configured to bear on said dropping platform, along an axis perpendicular to the plane and through said shock-absorbing element. According to one feature, the inflatable lifting cushion is a pneumatic inflatable lifting cushion, particularly easy to implement, for example using a simple air compressor for inflation. According to one feature, the assembly further comprises a spreader pad to distribute a force of the lifting device on said shock-absorbing element and thus offering better shock-absorbing. According to one feature, the assembly further comprises an interface element between the lifting device and said payload, thus limiting the risks of damaging the payload and offering better shock-absorbing. According to one feature, said shock-absorbing element is a viscoelastic shock-absorbing element. According to one feature, said guiding element comprises an oblong opening for accessing said filling element, facilitating access to said filling element regardless of the filling state of said inflatable lifting cushion. According to another aspect, an object of the invention is a method for protecting a payload, the method comprising: - installing said payload on a dropping platform; - establishing, between said payload and said platform, at least one shock-absorbing assembly as described before; - at least partially filling said inflatable lifting cushion; and - securing said payload to said platform. Thus, the method according to the invention allows absorbing the shock of a payload such as a vehicle upon an impact, in particular an impact upon landing following a drop, for example by an aircraft. It makes simple and economical the establishment of the payload possible, for example with the help of one single operator and a simple compressed air compressor, without the need for special handling means. According to another feature, the method comprises, after filling said inflatable lifting cushion, closing a filling valve. Still according to another aspect, an object of the invention is a method for recovering a payload, from a dropping platform, said payload resting on at least one shock-absorbing assembly as described before, the method comprising: - at least partially emptying the inflatable lifting cushion of said at least one shockabsorbing assembly; - removing said at least one shock-absorbing assembly; and - extracting said payload from said platform. The method according to the invention allows absorbing the shock of a payload such as a vehicle upon an impact, in particular an impact upon landing after a drop, for example by an aircraft. It allows easy and cost-effective recovery of the payload, for example with the help of one single operator. According to one feature, said emptying of said inflatable lifting cushion comprises opening a filling valve. Brief description of the drawings Other aims, features and advantages of the invention will become apparent upon reading the following description, given merely as a non-limiting example, and made with reference to the appended drawings, wherein: [Fig. 1] schematically shows a vehicle mounted on a dropping platform in view of dropping it from an aircraft, according to embodiments of the invention; [Fig. 2] illustrates a sectional view of an example of a shock-absorbing system, in a configuration enabling the movement of a payload to be protected, according to embodiments of the invention; [Fig. 3] illustrates a sectional view of an example of a shock-absorbing system, in a configuration enabling the protection of a payload upon an impact, according to embodiments of the invention; [Fig. 4] illustrates an exploded view of an example of lifting device as illustrated in Figures 2 and 3; [Fig. 5] illustrates an example of steps of packaging a vehicle in view of dropping it by an aircraft, according to embodiments of the invention; and [Fig. 6] illustrates an example of steps of unpackaging a vehicle dropped by an aircraft, according to embodiments of the invention. Detailed disclosure of at least one embodiment A detailed description of particular embodiments of the invention will be provided below, referring to the drawings wherein the same references identify the same structural elements in each of the figures. Figure 1 schematically shows a vehicle mounted on a dropping platform in view of dropping it from an aircraft, according to embodiments of the invention. As illustrated, the assembly 100 here comprises a dropping platform 105, also called an airdropping platform when used to drop a payload such as a vehicle from an aircraft, and a vehicle 110. The assembly 100 further comprises a structure 115, fastened to the dropping platform 105, on which one or more fall control and deceleration systems 120 are placed, for example one or more parachutes. According to embodiments, the deceleration and fall control system(s) are attached to the dropping platform 105 in order to slow down the lowering of the dropping platform 105. The assembly 100 also comprises shock-absorbing assemblies 125-1 and 125-2, generically referenced 125, as well as restraining elements 130, for example straps, for fastening the pay load, here the vehicle 110, to the dropping platform 105. It is observed here that the number of shock-absorbing assemblies depends on the features of these assemblies and the features of the pay load, particularly the weight thereof and the weight distribution. To ensure payload stability, at least three shockabsorbing assemblies are used. For one vehicle, four shock absorber assemblies can be used to support the front and rear, on each side. Additional shock-absorbing assemblies may be used, for example at the front or at the rear, depending on the cantilever and weight distribution. Examples of shock-absorbing assemblies are described with reference to Figures 2, 3 and 4. Figure 2 illustrates a sectional view of an example of shock-absorbing system 125, in a configuration making it possible to move a payload to be protected, according to embodiments of the invention. Figure 3 illustrates a similar sectional view, in a configuration enabling the protection of the payload. As illustrated, the shock-absorbing system 125 is positioned between a dropping platform 105 and a payload such as the vehicle 110. It comprises a shockabsorbing element 135 and a lifting device 140. For example, the shock-absorbing element 135 is a foam such as a viscoelastic foam. The aim is to absorb the kinetic energy transmitted by the payload. According to the illustrated example, the shock-absorbing element extends over the dropping platform 105, between the dropping platform 105 and the lifting device 140. According to some embodiments, a spreader pad 145 is used between the shock-absorbing element and the lifting device to distribute the kinetic energy transmitted by the payload over a large surface of the shock-absorbing element. According to other embodiments, the shock-absorbing element is disposed between the lifting device and the payload. For illustration, the shock-absorbing element 135 is a viscoelastic foam manufactured from polyurethane. Still according to particular embodiments, an interface element 150 is interposed between the lifting device 140 (or, where applicable, the shock-absorbing element) and the payload, for example the vehicle 110. This interface element makes it possible to distribute the forces transmitted by the payload on the lifting device whose upper surface is, according to particular embodiments, flat. Thus, the interface element may comprise a flat lower face and an upper face conforming to the shape of the payload. According to particular embodiments, the interface element comprises a deformable material, such as a foam, to conform to the shapes of the payload, at the location where it bears thereon. Again, it may be a polyurethane foam. According to the example illustrated in Figures 2, 3 and 4, the lifting device comprises a guiding element 155 provided with a cylindrical cavity extending along a longitudinal axis substantially perpendicular to the plane of the dropping platform 105. This cylindrical cavity is at least partially closed at one of the ends thereof, here in the upper part thereof, along a plane substantially parallel to the plane of the dropping platform 105. The lifting device also comprises a sliding element 160, configured to slide in the cylindrical cavity of the guiding element 155, along a longitudinal axis of the cylindrical cavity. The sliding element 160 extends outside the cylindrical cavity, opposite the closed end of the cylindrical cavity. Moreover, the lifting device comprises an inflatable lifting cushion 165 arranged in the cylindrical cavity, between the closed end of the cylindrical cavity and the sliding element. As described with reference to Figure 4, the inflatable lifting cushion comprises a filling, closing and emptying element 170. When the inflatable lifting cushion is in an empty or partially empty state, the guiding element 155 is in a low position due to the weight thereof, as illustrated in Figure 2, preferably without contact with the payload. The payload can then be freely handled, particularly to be installed on the dropping platform or to be extracted from this platform. When the inflatable lifting cushion is in an inflated or partially inflated state, increasing the volume thereof moves the sliding element away from the closed end of the cylindrical cavity, driving the guiding element into a high position and lifting the pay load if placed on the lifting device, as shown in Figure 3. The pay load is then protected, in case of a vertical or essentially vertical impact, by the combined effect of overpressure in the lifting cushion and the shock-absorbing element, which is exerted on the payload at the bearing point of the lifting device (or the shock-absorbing element where appropriate). This bearing point is selected according to the features of the payload. It is usually provided by the payload manufacturer. Figure 4 illustrates an exploded view of an example of lifting device as illustrated in Figures 2 and 3. According to this example, the guiding element 155 comprises a ring or body 155-1 and upper plate or closing part 155-2 fastening to the ring, for example by screwing. The ring 155-1 comprises a cylindrical cavity, here having a square base. The upper plate here corresponds to the closed end of the previously targeted cylindrical cavity. The ring further comprises, in its lower portion, an opening 155-3, preferably central, enabling the passage of the sliding element 160 as well as an oblong opening 155-4, herein at an angle, to access the filling, closing and emptying element 170 of the inflatable lifting cushion 165, whether the guiding element is in its low position or its high position. The inner sides of the ring 155-1 measure for example between 100 mm and 1,500 mm, for example 200 mm. For example, its height is between 50 mm and 300 mm, it is for example 130 mm. Other ring shapes may be used. For example, the ring 155-1 and the upper plate 155-2 may be made of aluminium, for example aluminium 6082 with a thickness between 5 and 20 mm. Still according to the illustrated example, the sliding element 160 comprises two portions: an inflatable lifting cushion support comprising a body 160-1, a bearing part 160-2 and a lower plate 160-3. The body 160-1 is here formed of a cylinder whose shape and dimensions of the base correspond substantially to the opening 155-3 of the ring 155-1 of the guiding element 155, such that the body 160-1 slides freely in the opening 155-3. The shape and dimensions of the bearing part 160-2 substantially correspond to the base of the cylindrical cavity of the guiding element 155, such that the bearing part 160-2 slides freely in the cylindrical cavity of the guiding element 155. The lower plate 160-3 is fastened to the body 160-1, for example by screwing, after mounting the sliding element 160 in the guiding element 155. By way of illustration, the height of the body 160-1 may be substantially equal to the height of the ring 155-1. Like the parts of the guiding element 155, the parts of the sliding element 160 may for example be made of aluminium, for example aluminium 6082. The inflatable lifting cushion 165 may for example withstand a load of less than 5 tonnes, for example a load of 3 tonnes, may withstand a maximum pressure of 12 bars, may have a height stroke capacity of less than 250 mm, for example 115 mm, may have a thickness between 5 and 30 mm, for example 20 mm, and / or may be square in shape with, for example sides with a length between 100 mm and 1,500 mm, for example 200 mm. The shape and the size of the inflatable lifting cushion correspond, preferably in a horizontal plane, to those of the base of the cylinder corresponding to the cavity formed by the ring 155-1 such that the inflatable lifting cushion occupies the entire space between the upper plate 155-2 and the bearing part 160-2. For example, the inflatable lifting cushion is made of a reinforced aramid web, coated with a hot-vulcanised elastomer. As previously described, the inflatable lifting cushion 165 comprises a filling, closing, and emptying element 170. It is herein positioned in a corner of the inflatable lifting cushion. It may comprise a valve, for example a brass valve which can operate with a maximum pressure of 20 bar and offering a maximum flow rate of 1.4 m3 / h. Inside the inflatable lifting cushion, this valve may be extended by a tubular part to inject a fluid, for example air, into the inflatable lifting cushion. Outside the inflatable lifting cushion, this valve may be extended by a connector or a valve provided with an endpiece, preferably standard, to be connected, for example, to a compressor. According to other embodiments, the lifting device 140 consists essentially of an inflatable lifting cushion, for example similar to the inflatable lifting cushion 165. Figure 5 illustrates an example of steps of packaging a vehicle in view of dropping it by an aircraft, according to embodiments of the invention. As illustrated, the aim of a first step (a) here is to bring the vehicle 110 onto the dropping platform 105, to the location it must have to be transported. In a second step (b), shock-absorbing assemblies are positioned under the vehicle. By way of illustration, four shock-absorbing assemblies can be positioned, one at the front left referenced 125-1, one at the rear left, referenced 125-2, one at the front right (not visible) and one at the rear right (not visible). These shock-absorbing assemblies may be similar to those described with reference to Figures 2, 3 and 4. A different number of shock-absorbing assemblies can be used. This number may particularly be determined according to the features of the latter, in particular the lifting capacity thereof, and those of the pay load, in particular the weight thereof. It is observed here that one or more shock-absorbing assemblies according to the invention can be used in combination with known systems, for example one or more cardboard stacks. In a next step (c), the inflatable lifting cushion of each shock-absorbing assembly is inflated, for example with air and using a compressor 500. The filling, closing and emptying element of the lifting cushion is then actuated to close it. The inflation pressure is determined according to the features of the shock-absorbing assemblies and the weight of the vehicle 110. According to particular embodiments, a plurality of shock-absorbing assemblies are connected together, at the filling, closing and emptying elements, to make it possible to inflate the inflatable lifting cushions simultaneously. Afterwards, the vehicle is secured (step (d)) to the dropping platform, for example using straps 130. Figure 6 illustrates an example of steps of unpackaging a vehicle dropped by an aircraft, according to embodiments of the invention. When the assembly comprising particularly the dropping platform 105 and the vehicle 110 lands after being dropped (step (a)), the vehicle is detached, for example by removing the straps 130 (step (b)). It should be herein observed that the absorption of the shock, upon landing, is ensured by the combination of an overpressure in the lifting cushions and by the shock-absorbing elements, for example made of viscoelastic foams, which accept deformation in all directions. 5 In a next step (step (c)), the inflatable lifting cushion of each shock-absorbing assembly is deflated, for example by actuating the filling, closing, and emptying element of the inflatable lifting cushion to open it, for example by turning a filling / emptying valve. Again, according to particular embodiments, a plurality of shock-absorbing 10 assemblies are connected together, at the filling, closing and emptying elements, to make it possible to deflate the inflatable lifting cushions simultaneously. For example, the filling, closing and emptying elements can be connected to a common valve. The shock-absorbing assemblies are then removed (step (d)) and the vehicle is extracted from the dropping platform (step (e)), for example forward, by rolling. 15

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