FR2886916A1 - SLIDING FLOAT COMPRISING A SANDWICH STRUCTURE BRIDGE WITH ELASTIC SHAPE - Google Patents

Abstract

The invention proposes a water slide float, of the type comprising a core (14) covered by an outer casing (12) forming a bridge and a hull, of the type in which the outer casing (12) comprises at least a bridge portion and a hull portion, of the type in which at least the bridge portion of the envelope comprises a sandwich structure comprising at least one low density core layer (24) between two thinner layers and with high mechanical characteristics (26 , 28), and of the type in which the high mechanical performance layers (26, 28) comprise resin impregnated fiber plies, characterized in that the low density center layer (24) of the bridge portion comprises a cellular material flexible and elastic.

Description

SLIDING FLOAT COMPRISING A SANDWICH STRUCTURE BRIDGE WITH ELASTIC SHAPE

  The invention relates to the field of floats gliding on water, such as surf floats or windsurfing.

  Traditionally, a surf float is made from a foam roll, including rigid polyurethane foam, which is formed in a mold. The foam roll is machined by planing and sanding to locally customize its shape and form the core of the float. This core is then coated with a resin-impregnated glass fiber shell which forms an outer reinforcing shell and gives the float its final shape and mechanical strength. A decoration and an icing give the float its final appearance.

  In some cases, the core is cut longitudinally into two parts which are then glued against a wooden lath which reinforces its structure.

  One of the disadvantages of such a construction technique is the final weight of the float. Indeed, the foam is relatively dense: typically its density is 50 kg / m3. And it is not possible in principle to reduce the density of the foam without affecting the mechanical characteristics of the float.

  In the field of boogie boards, the float is essentially composed of elastic foam (possibly by combining several layers of different densities and characteristics), without the presence of an envelope with high mechanical characteristics. In some cases, these floats are provided with a lower layer of thermoformed plastic to ensure better glide on the water. However, these boards are generally relatively flexible because the user must be able to deform them in use to maneuver at best. Unlike surfboards and windsurfers, where the user is standing, boogie boards must not withstand great effort because the user uses them while lying on the surface of the water, with only his bust resting on the board.

  According to another technique of construction from the field of windsurfing, starting from a rigid foam roll of relatively low density (for example an expanded polystyrene foam of 18 kg / m3) that is machined so as to shape it, or mold directly to the shape of the float core. This core is covered with an outer shell, which may comprise a resin impregnated glass fiber skin, and / or a thermoformed plastic sheet, and / or a sandwich structure. Such a construction method can allow weight gain while maintaining good rigidity, especially when using a sandwich structure envelope, that is to say a structure comprising a low density layer (usually PVC foam or extruded polystyrene) between two thinner layers with high mechanical properties (especially resin-impregnated fibers). Such a construction, when it makes use of sandwich structures, makes it possible to obtain stiff boards, therefore potentially powerful, but sometimes at the cost of a lack of comfort, and a lesser ease of driving.

  According to still other techniques, the float is composed of a central core made of a first cellular material, which is covered with a layer of rigid cellular material, denser and more resistant, itself covered with an outer skin (Thermoformed plastic sheet or resin-coated fiber layer, see WO-82/04023 or DE-33.11.734).

  It is also known to make hollow floats with a sandwich structure envelope. One can for example make two half-shells which are then assembled together, or even achieve all in a closed mold with an internal bladder that is inflated to push and apply the sandwich structure against the walls of the mold.

  In another register, it is known to produce floats which comprise a rigid internal structure covered with an outer layer of flexible foam, which determines the external shape of the float (US-3,543,315 or US-5,489,228). These floats are generally very comfortable in navigation but, their weight is too important and the flexibility of the outer shell does not give good results in terms of nervousness and precision driving the board. Indeed, the layer of flexible foam is only covered with a plastic film or a flexible coating having no notable mechanical strength and whose only role is to protect the flexible foam abrasion and improve the slips.

  Moreover, it is known to propose floats which have a different structure on the hull and on the deck. In document FR-2. 787.088, it is proposed a float comprising a foam core which is covered with an envelope. On the deck, the shell is a rigid sandwich structure while on the hull the shell is a single layer of resin impregnated fibers. In the document FR-2.612.874, the hull of the float is covered with a thin layer of elastic material so as to impart shock absorption properties. On the contrary, in DE-32.06.334, it is the deck of the float which is covered with a layer of elastic material. In the last two cases, the layers of elastic material are directly exposed to the outside.

  The document DE-197.41.917 describes several constructions in which the envelope of the float comprises a resin-impregnated fiber layer associated with a layer of damping material. Various possibilities are provided but it is always expected that the damping layer is arranged outside with respect to the resin-impregnated fiber layer.

  On the other hand, it is intended that the damping layer may be arranged either on the deck or on the deck and on the hull. This document does not plan to use a sandwich structure envelope.

  The object of the invention is to propose a new construction optimized for the production of a gliding float, particularly for the practice of surfing or windsurfing, which is particularly optimized to guarantee ease of implementation suitable for to allow a low cost, a limited float final weight, a sufficient overall stiffness to obtain an adequate level of performance, and a certain comfort of use, without sacrificing either the float's driving precision, or its solidity.

  For this purpose, the invention proposes a float for sliding on the water, of the type comprising a core covered by an outer shell forming a bridge and a hull, of the type in which the outer envelope comprises at least one bridge portion and one hull portion, of the type in which at least the bridge portion of the envelope comprises a sandwich structure comprising at least a central layer of low density between two layers of finer and high mechanical characteristics, and of the type in which the layers at high Mechanical performances comprise resin-impregnated fiber plies, characterized in that the low density central layer of the sandwich structure of the bridge portion comprises a flexible and elastic cellular material.

  In an improved embodiment of the invention, there is provided a float glide on water, of the type comprising a core covered by an outer casing forming a bridge and a hull, of the type in which the outer casing comprises the at least one bridge portion and one hull portion, both made in the form of a sandwich structure composed for each of the parts of at least one central layer of low density between two layers with finer and high mechanical characteristics, of the type in wherein the high mechanical performance layers comprise resin impregnated fiber plies, characterized in that the low density core layer of the hull portion is made of rigid cellular material while the low density core layer of the bridge portion comprises a flexible and elastic honeycomb material.

  Other features and advantages of the invention will appear on reading the detailed description which follows, as well as on the view of the accompanying drawings, in which: FIG. 1 is a schematic view from above of a float according to a improved mode of the invention; - Figure 2 is a schematic cross-sectional view along line IIII of the float of Figure 1; - Figure 3 is a partial view of Figure 2, enlarged and exploded; - Figure 4 is a schematic cross-sectional view illustrating an embodiment of a stiffening reinforcement.

  In Figure 1, there is illustrated the general external shape of a gliding float on the water 10, for example a surf float. In Figure 2, there is illustrated an embodiment of the invention wherein the float comprises a core 14 arranged inside an outer casing 12. In known manner, the outer casing 12 hay, in its part upper deck 16 of the float on which the user is intended to bear, and in its lower part, the hull 18 which is supported on the water. The peripheral side edge of the outer envelope defines the float rails. Of course, this outer envelope defines, in a sealed manner, an internal space of the float which is wholly or partially filled by the core 14.

  It is conceivable, for the realization of the core, to use an expanded polystyrene foam of very low density, for example of a bulk density of less than 25 kg / m3 or even equal to or less than 18 kg / m3.

  The core 14 may also include localized reinforcements particularly resistant material, extending over the entire height of the internal space defined by the envelope, or only a portion of this height. An embodiment of such a core will be described below with reference to FIG. 4.

  In the example illustrated, the core 14 completely fills the internal space of the float. However, it may be provided that it comprises recesses so as to leave, inside the outer casing 12, hollow internal zones, for example at the front of the float, zone on which the user generally takes very little support. The presence of hollow zones will of course have a favorable influence on the weight of the float and their distribution will influence the moment of dynamic moment of inertia of the float, which will influence its behavior on the water, notably its response to the different supports and changes of directions. imposed by the user.

  For the sake of simplicity and economy, the core 14 illustrated in the figures is monobloc and composed of a single material. However, it could be expected that the core is composed of several elements, possibly made of different materials.

  In addition, it could be expected that the core is pierced with lightening holes. Similar methods for lightening the core, such as those described in FR-2.820.712, FR-2.820.713, and FR-2.820. 714, may be advantageously implemented in the context of the present invention.

  In this embodiment of the invention, the two parts (bridge and hull) of the envelope have a sandwich construction in which a layer of low density material, forming the core 24, 25 of the sandwich structure, is imprisoned between two inner and outer layers 26 of reinforcing material which form the skins of the sandwich and which comprise, for example, layers of fibers embedded in a resin, for example an epoxy resin. The nature of the fibers (glass, carbon, aramid, etc.) may be identical or different for the inner layer or for the outer layer. Similarly, it may differ between the hull portion 30 and the bridge portion, that is to say it may for example be provided that the inner layer of the bridge portion comprises aramid fibers while the inner layer the hull portion would include carbon fibers. Similarly, the layers of fibers may be woven or non-woven, unidirectional or multidirectional. For the simplest and most economical constructions, the layers of fibers will be fiberglass fabrics.

  However, in this improved embodiment of the invention, the two parts of the bridge and hull of the envelope differ in the nature of the material which constitutes the core 24, 25 of their sandwich structure. In the hull portion, the layer of low density material 25 consists of one or more materials qualified as rigid, while in the bridge portion the layer of low density material 24 comprises, in accordance with the invention, the at least one part made of a flexible cellular material.

  Of course, the low density materials will preferably be cellular materials, including foams of plastics.

  The person skilled in the art has the habit of classifying foams made of plastic material in flexible foams on the one hand and in rigid foams on the other hand.

  Rigid foams have a low elasticity in that as soon as the compression force exceeds a certain value, they deform by collapse, irreversibly or very little reversible. Rigid foams include polyurethane foams and extruded polystyrene or expanded polystyrene foam which are generally used in the form of foam bars to form the cores of traditional surfboards. Similarly, some PVC or polyimide foams commonly used as core in sandwich structures are considered rigid materials. Although called rigid, these foams can, in the lowest densities, be quite easily compressible (and therefore appear soft), but they have a very low elasticity.

  Among the flexible cellular materials, resilient plastic foams with an elastic nature are known, such as expanded polyolefin foams, in particular polypropylene or polyethylene foams. In the case of expanded polypropylene foams, it is possible, for example, to use grades having apparent densities of between 20 and 100 kg / m 3. These materials generally have a stress at 25% of compressive strain of the order of 100 to 600 kPa. The principal elements of choice of the material will be its stiffness to the compression, but still more its capacity of elastic deformation (the material will preferably have to recover its initial form after a compression of the order of 25%), and its capacity of restitution of the energy absorbed during compression.

  Of course, other materials can be used. Thus, for the hull, the rigid foam 25 may be replaced by a honeycomb structure, or by a light wood layer.

  The fact of using a rigid core 25 for the sandwich structure of the hull allows in particular to obtain a high rigidity of the hull, favorable to good acceleration and very good precision driving the board. In less elaborate embodiments of the invention, the hull portion of the envelope may have another structure. It may be a single layer of resin-impregnated fibers, or an intermediate layer of a light and rigid material (rigid foam, light wood, etc.) 3 5 covered with a layer of fibers impregnated with resin.

  The use of a flexible material to form the core 24 of the sandwich structure of the bridge is particularly innovative. Indeed, by choosing the right stiffness for this flexible material, it will be possible both to benefit from the exceptional rigidity / weight ratio of the sandwich structure, while introducing at the level of the deck a surface flexibility particularly pleasant in terms of comfort and ease of driving the float.

  This is due to the fact that the outer skin of resin impregnated fibers 28, which inherently has strong elastic properties, will be able to deform under the support of the user without causing the collapse of the core material 24, also elastic , then return to position by restoring a large part of the energy stored. The outer skin 28 is then stressed both in flexion and in traction along its plane, like a trampoline. Thus solicited, the outer skin 28 of composite material allows a much greater energy return than the simple springback of an elastic material that would be disposed on the deck of the float and which would be compressed vertically. In comparison, the trampoline effect, with a high elastic component, can be opposed to a simple mattress effect which is essentially damping, and which therefore tends to restore only a small part of the energy communicated to it. The trampoline effect makes driving the float much more lively.

  Of course, this effect of deformation / restitution of the outer skin 28 of the sandwich is perfectly reversible (at least up to a certain limit that can be determined for example by varying the thickness and stiffness of the outer skin 28 and / or by varying the stiffness of the elastic flexible material forming the core 24 of the sandwich structure) and it takes place without causing significant deformation of the core 14, thanks to the presence, under the flexible and elastic layer, of the layers This fiber, in addition to its own mechanical strength, makes it possible to distribute over a large area the stresses transmitted to it.

  In addition to the advantage in terms of liveliness, the elastic core sandwich construction allows the bridge to better withstand shocks and driving effects. To improve the trampoline effect, the resin of the outer skin (for example an epoxy resin) may optionally be mixed with compounds which improves its flexibility.

  In the illustrated example, it can be seen that the flexible foam layer 24 which forms the core of the sandwich structure of the bridge extends down along the lateral edges of the float. This in particular makes it possible to benefit from the best impact resistance of this structure in a particularly exposed area. Of course, it could also be provided that it is the sandwich structure of the hull that rises along the side edges, that the two structures meet at the point of greater width, or that the side edges have a clean structure.

  Several methods can be envisaged to ensure the production of a float according to the invention.

  The outer casing 12 may be made in the form of two prefabricated half-plates, forming respectively the bridge and the hull, the half-shells being assembled to one another, for example by gluing along their joining plane, to form a sealed outer envelope.

  Alternatively, the two half-shells can be joined to each other before the outer reinforcing layer is applied to the core-forming layer of the sandwich. Such a method is similar to that described in WO-02/10011, which will be usefully referred to, and has the advantage of allowing the opportunity to rework the core layer of the sandwich, after assembling the half -coques, but before the laying of the outer layers of the sandwich, this in order to customize the shape of the float, if this is desirable.

  According to another method of construction, all the components can be assembled and shaped under pressure in a mold, according to the technique usually used for the manufacture of windsurfing floats sandwich type.

  In the example illustrated in the figures (see FIG. 3), it is provided that the outer casing 12 furthermore has an external protection made in the form of a sheet of thermoformed thermoplastic material 30. This protective layer 30 is translucent example and it can be decorated. The decoration will advantageously be arranged on the face of the sheet which is turned towards the inside and it may be made for example by screen printing or by sublimation. It is also conceivable to incorporate a decorative element between the outer skin 28 and the protective sheet. The protective sheet will for example be made of a material comprising a mixture of ABS and polyurethane, and having a thickness of the order of 0.3 mm. Optionally, the sheets of protections could be different for the deck and for the hull. It can also be envisaged that such a protective layer is disposed only on one side of the float, for example the bridge.

  In FIG. 4, an embodiment of a reinforcement 32 is illustrated. This reinforcement 32 is simply composed of a sheet of resin-impregnated fibers folded on itself to form a T whose vertical leg 34 is inserted in a groove 36 formed in the core 14, and whose horizontal portion 38 rests against an upper face of the core 14. To do this, there is arranged in the core a rectilinear groove 36 substantially perpendicular to the outer face of the core. Then, the sheet of resin impregnated fibers (not yet polymerized, therefore still flexible) is folded in half and inserted at the bottom of the groove 36. The parts of the sheet which protrude outside are then folded against the outer face of the groove. core. Once the resin has polymerized, the reinforcement 32 forms a rigid T-shaped section which is integrated in the core 14. The vertical portion 34 of the T gives it a very good bending stiffness, while the horizontal part 38 forms a kind of plate The reinforcement 32 is particularly judicious on the bridge side of the float, because it reinforces the core where the high pressures due 'user. In Figure 1, there is illustrated a possible arrangement, with two reinforcements 32 disposed on the bridge, each of a median longitudinal axis of the board. One could also use such a type of reinforcement hull side, to take full advantage of its stiffness to bending.

  In the example of Figure 4, the reinforcement 32 is placed on the core 14 naked. However, to facilitate the operation, it may be preferable to set up the reinforcement after having coated the core of the inner skin 26. The main difference will be that the horizontal portion 38 of the T of the reinforcement will then be arranged between the inner skin 26 and the low density layer 24, 25.

  The construction according to the invention therefore makes it possible to achieve a float having a perfect compromise between ease and precision of driving, comfort and performance, all with a perfectly industrial process allowing relatively low costs.

Claims (2)

9 CLAIMS   1. Float slide on water, of the type comprising a core (14) covered by an outer casing (12) forming a bridge and a hull, of the type in which the outer casing (12) comprises at least one bridge portion and a hull portion, of the type in which at least the bridge portion of the envelope comprises a sandwich structure comprising at least one low density core layer (24) between two thinner layers with high mechanical properties (26, 28) , and of the type in which the high mechanical performance layers (26, 28) comprise resin impregnated fiber plies, characterized in that the low density central layer (24) of the sandwich structure of the bridge portion comprises a material soft and elastic alveolar.   2. Glide float according to claim 1, characterized in that the low density core layer (24) of the bridge portion of the envelope comprises a polyolefin foam.   3. Glide float according to claim 2, characterized in that the low density core layer (24) of the bridge portion of the envelope comprises a polypropylene foam.   4. Glide float according to any one of the preceding claims, characterized in that the material of the low density core layer (24) of the bridge portion of the envelope has a stress at 25% of compression deformation. of the order of 100 to 600 kPa.   5. Slide float according to any one of the preceding claims, characterized in that the material of the low density core layer (24) of the bridge portion of the envelope returns to its original shape after a compression of the order of 25%.   6. Glide float according to any one of the preceding claims, characterized in that the sandwich structure of the bridge portion (26, 24, 28) extends downwardly along the lateral edges of the float.   Sliding float according to any one of the preceding claims, characterized in that the sandwich structure (26, 24, 28) of the bridge portion of the envelope is covered with a protective layer (30) of plastics material. thermoformed.   Sliding float according to claim 7, characterized in that the protective layer (30) is transparent, and in that it is decorated on an inner face.   9. Glide float according to any one of the preceding claims, characterized in that the hull portion of the outer casing comprises a sandwich structure comprising at least one central layer of low density (25) between two thinner layers and to high mechanical properties (26, 28), in that the high mechanical performance layers (26, 28) comprise resin-impregnated fiber plies, and in that the low-density core layer (25) of the hull portion is made of rigid material.   10. Gliding float according to any one of claims 1 to 8, characterized in that the hull portion of the outer casing comprises at least one layer of resin impregnated fibers which covers an intermediate layer of rigid material.   11. Sliding float according to any one of the preceding claims, characterized in that the core (14) is made of expanded polystyrene foam.   12. Sliding float according to any one of the preceding claims, characterized in that the core (14) has recesses.   13. Slide float according to any one of the preceding claims, characterized in that the entire float is covered with a protective layer (30) of thermoformed plastic material.   14. Floating slide according to claim 12, characterized in that the protective layer is transparent, and in that it is decorated on an inner face.