FR2731160A1 - METHOD FOR MANUFACTURING A MOLDED STRUCTURE, IN PARTICULAR SKI OR SNOW-SURFING, BY INJECTION OF "IN SITU" EXPANSION FOAM - Google Patents

Abstract

A method of manufacturing a molded structure in the form of an elongated beam consisting of; - Arranging in a mold a lower sub-assembly comprising a sliding sole (3) bordered on either side by side edges optionally a lower reinforcement element (5); - Covering the lower sub-assembly with a covering sheet (8), to form a closed volume, intended to constitute the top and at least part of the side faces of said structure; - to close the mold; - Then in injecting into the volume thus defined the reactants of a foam (9) which expands 'in situ'; - then opening the mold to remove the complex molded structure, characterized in that at the time of molding, it is interposed between said lower sub-assembly (3, 5) and said cover sheet (8), several local bracing pieces, longitudinally distributed over at least part of the length of the molded structure; said parts being spaced from one another, resting on the lower sub-assembly and holding in place several local reinforcing elements (7) of small width, spaced laterally from one another over the width of said structure to mold.

Description

The invention relates to a method for manufacturing a molded structure

  having the shape of an elongated beam. More particularly, it relates to the manufacture of skis, snowboards and other similar machines adapted to skiing.

on the snow and on the ice.

  The present molded structures generally include various elements assembled in a homogeneous manner and whose role is to ensure the essential functions of mechanical resistance, sliding, attachment and protection of the structure. To obtain these functions, very diverse materials are used which have very different affinities or bonding compatibilities between them. The general problem is to achieve a perfect cohesion of the structure, which aims to meet the strength requirements due to the mechanical constraints imposed by the use, while decreasing the number and duration of manufacturing steps. In addition, structures are associated with increasingly complex external shapes to increase the attractiveness of the products. In response to this problem, the injection technique in situ is frequently used. It consists, generally in a first step, to dispose against or near the walls of the cavity of a mold, the peripheral elements of the structure, more particularly; the sliding sole, the side edges, the upper and lateral protective envelope, the reinforcing elements and other elements. Then, in the volume thus formed, the constituents of a curable foam such as a polyurethane or phenolic foam which expands and ensures both the plating of the peripheral elements against the walls of the mold and the assembly of at least part of the elements between them. Such a process is described indifferently in French Application Nos. 2,654,645 or 2,654,670, for example. As these requests teach, it is however necessary to use a tubular sheath based on bonding films whose role is on the one hand, to achieve a sealed screen between the foam and the components of the resin reinforcements and on the other hand, to ensure the adhesion of the foam with the resin of the peripheral reinforcements to avoid delamination of the structure. The reinforcements used are in the form of textile webs pre-impregnated with thermosetting resin or pre-glued metal plates. We obtain very homogeneous and resistant final structures but which are also very expensive

  given the materials and the manufacturing technique used.

  The document FR 2 679 780 avoids the use of adhesive films and proposes to replace the reinforcing elements with a tubular sheet in the form of a mesh network in order to define a closed interior compartment in which the constituents of the foam are injected. . Thus, the foam passes through the mesh of the tube to coat it, and to press the upper face and the side faces of a cover layer of flexible thermoplastic material against the walls of the mold. It is obvious that such a tube does not provide optimal reinforcement of the structure given its own structure and its approximate placement inside the ski after injection. In addition, the tube must have a thickness that adapts to the thickness distribution of the ski. At a given size and distribution of thickness corresponds a particular tube reference. The

  reference number is multiplied and therefore production costs are higher.

  In addition, the mesh tube remains relatively flexible and therefore plays a minor role in maintaining the peripheral elements before foaming. It does not participate more in the forming of the covering layer which must therefore be

  flexible enough to be deformed by the pressure of the foam.

  Document FR-A-2 700 479 relates to an improvement which consists in adding an additional reinforcement of dry fabric reinforced with metal weft threads to obtain an inverted U-shaped curvature in the area of the

skate only.

  Its function is to improve the reinforcement and the transmission of the supports on the edges in the zone of the skate. In this zone, it favors the maintenance of the elements. However, such a structure keeps in the other parts of the ski

  the aforementioned drawbacks of the perforated sheath.

  Japanese Patent (B2) No. 63-63233 relates to a method of manufacturing skis by injecting a synthetic foam inside a structure using openwork reinforcements based on fibers and resin disposed on the surface of the soleplate. and on the underside of the upper decorative layer. The upper reinforcement is supported by several sections of corrugated sheets of elastic material longitudinally spaced along the entire length of the ski. The method applies to the manufacture of sandwich skis; that is to say comprising a stack of flat plates of different elements comprising the sole, the lower reinforcement, the core, the upper reinforcement and the decoration top. The foam is simply used to glue the different elements as it can

  penetrate through the mesh of reinforcements.

  DE-A1-43 19 245 relates to a method of manufacturing a ski by injection of a foam. The upper reinforcement may be a perforated steel plate held in position along its width by several spacer pieces. These parts, however, have the sole function of maintaining the perforated plate in contact with the lower surface of the outer layer of the ski without spares determined space for sufficient passage of the foam to ensure a perfect adhesion and a good forming the outer layer. The outer layer is

  in a flat configuration and maintained in a sliding air gap of the mold.

  It is the pressure of the foam that deforms the outer layer and performs its forming against the walls of the mold. The positioning of the reinforcement plate during injection is therefore rather random since it is simply maintained in pressure by the spacer parts against the outer layer which is deformed. The object of the present invention is to provide an improvement to the existing injection processes for producing a ski shaped and economically. One of the objects is therefore to achieve the assembly, the bonding of the elements and the forming of the outer covering sheet by the foam injected 'in situ' at

  during a single main injection cycle.

  Another object of the invention is the possibility of avoiding any interface of

additional collage.

  Another object of the invention is to be able to vary the mechanical characteristics of the ski easily in a flexible way according to the needs and

economical way.

  Another object of the invention is to retain a wide choice of materials used to form the reinforcing elements, compatible with the bonding with the

foam.

  Another object of the invention is to ensure excellent positioning of the reinforcing elements during the injection to ensure characteristics

  mechanical reproducible and controlled.

  Another object of the invention is to facilitate the implementation of the elements by

  the manipulator thus saving time and productivity.

  For this the invention relates to a method of manufacturing a molded structure having the shape of an elongated beam consisting; - To have in a mold a lower subassembly comprising a gliding sole bordered on either side by lateral edges possibly a lower reinforcement element; - Covering the lower subset of a cover sheet, to form a closed volume, intended to form the top and at least part of the side faces of said structure; - to close the mold; then injecting into the volume thus defined the reagents of a foam that expands 'in situ'; - Then to open the mold to remove the complex molded structure, characterized in that at the time of setting into the mold, is interposed between said lower subassembly and said cover sheet, several local pieces of bracing, longitudinally distributed over at least part of the length of the molded structure; said pieces being spaced apart from each other, resting on the lower subassembly and holding in place a plurality of local reinforcing members of small width, laterally spaced apart from each other across the width of said molding structure; Thus, the foam serves both to form the structure, and in particular the cover sheet and the bonding of the essential elements of the structure between them. The lateral spacing of narrow reinforcements allows the foam to circulate

  more freely and promotes the cohesion of the whole structure.

  According to another characteristic of the invention, the bracing pieces locally support the cover sheet; and holding local reinforcing members in place at a predetermined distance from the bottom surface of said cover sheet to promote passage of the foam between the reinforcing members and said cover sheet. The forming and cohesion of the structure is further improved. The foam completely traps

  local reinforcement elements, which prevents any risk of delamination.

  According to another characteristic of the invention, the bracing pieces are obtained from one or more plastic or metal profiles made by injection, extrusion or pultrusion, then cut into lengths of length. determined. Thus, these parts can be obtained very economically. According to another characteristic of the invention, each bracing piece is in the form of a section of flattened tube whose wall comprises, at least, a series of open housings of concave cross-section and which extend substantially in the direction longitudinal of the molded structure, in which are inserted the local reinforcing elements. Thus, the prepositioning of the reinforcements is facilitated without particular adjustment on the part of the manipulator. The necessary predetermined distance is also provided between the elements of

  reinforcement and the cover sheet.

  The reinforcements are always inside the structure in the same configuration; which guarantees a good reproducibility of the characteristics

from one ski to another.

  According to a complementary feature, the cross section of each housing comprises a narrowing zone to allow clipping engagement of each local reinforcing element. Fixing each reinforcement is quick, simple and without bonding. The reinforcements can thus be slightly bent and prestressed to adapt to the particular geometry of the structure, while remaining firmly retained in their housing. We obtain

  also saves time in the prepositioning operation.

  According to another characteristic of the invention, each bracing piece is in the form of a profile section having a series of holes which extend substantially in the longitudinal direction of the molded structure, and whose cross section is slightly greater than the cross section of each local reinforcement element. In this case, the prepositioning is also very fast. The retention of the reinforcing elements can be done without bonding. According to another characteristic, the bracing pieces are made of a deformable semi-rigid material to adapt to the variation in thickness of the cross section as a function of the length of the molded structure. Thus, it is advantageous to limit the number of part references used along the molded structure since only one reference can adapt to the thickness profile.

  of the molded structure, in a given range of thickness.

  Alternatively, the bracing pieces are made of a rigid material resistant to crushing. In this case, on the contrary, the spacer part participates in the preforming of the cover sheet during the

closing the mold.

  According to another characteristic of the invention, the local reinforcing elements are circular, oval or polygonal solid section rods. Compared to traditional reinforcements plate, rushes are more economical. In addition, their use makes it possible to modulate more easily the mechanical characteristics of

flexion and torsion of the beam.

  Other features and advantages of the method of the invention will emerge

  of the description which follows with regard to the attached drawings which are not given

  by way of non-limiting examples: FIGS. 1 to 5 illustrate, by cross-sections, a first embodiment of the method of manufacturing the molded structure according to the invention; - Figure 6 shows a schematic longitudinal view of the molded structure; - Figure 7 shows a cross section of a variant of a molded structure according to the method of the invention; - Figure 8 shows a cross section of a second variant of a molded structure; - Figure 9 shows a cross section of a third variant of a molded structure; - Figure 10 shows a cross section of a fourth variant of a

molded structure.

  According to a particular embodiment of the method of the invention applied to the manufacture of a ski, is deposited flat and bottom of a lower portion (1) of a mold, respectively a gliding sole (3), for example made of polyethylene, two side edges (4) bordering on each side the gliding sole. The sole is then covered by a first lower reinforcement element, such as a metal plate (5). Preferably, the plate extends longitudinally continuously over a large part of the length of the structure to be produced. It advantageously comprises pins (50) evenly distributed on its lower surface which allow a setting of the plate on the sole while providing a space between the sole and the lower surface of the plate. At the point of the barbs, the upper surface of the plate also comprises punctured troughs, for example. The plate (5) then has a plurality of local bracing pieces (6); separated

  longitudinally one of the other over the entire length of the structure to achieve.

  In the case illustrated, each piece (6) is in the form of a hollow tube section whose lower part comprises pins (60) of complementary shape to that of the recesses (51) of the plate (5), to allow easy prepositioning of the local parts with respect to the plate (5). In the upper portion of the tube, the wall includes a series of laterally spaced, upwardly open housings (62) having a concave cross section. These upper housing (62) open upward extend over the entire

  length of each piece in the longitudinal direction of the molded structure.

  Then inserting in each housing, or in some of them only, as the case may be, a local reinforcing element (7), preferably a solid section rod. The rods are made of material chosen from the group consisting of a metal of the steel, aluminum or aluminum alloy type, a reinforced plastic material. In the illustrated example, each ring has a section of substantially circular shape, but one can imagine other sections of oval or

polygonal, for example.

  In order to facilitate the holding in position of each local reinforcement element (7) in its respective housing; it is expected that the cross section of each housing comprises a narrowing zone of width slightly smaller than the diameter of the reinforcing element. Engagement is done by clipping

  elastic by simple manual pressure.

  As shown in Figure 2, after placing the local reinforcing elements, the structure is covered by a plastic covering sheet (8), monolayer or multilayer. Such a sheet is generally chosen from soft or semi-rigid thermoplastic materials at ambient temperature. This sheet is slightly tiled by hand and then prepositioned, so that its lateral ends can take position in longitudinal grooves (10) of the lower part of the mold. Squeezable silicone seals (11) are provided to improve sealing after closure of the mold. Then, the upper part (2) of the mold is lowered to form a closed chamber sealed by compression joints (11). When closing the mold, the lateral edges of the cover sheet (8) are firmly gripped in the gap formed in the vicinity of the joint plane of the mold (100); without possibility of slipping of the sheet (Figure 3). Thus, it is necessary to provide that the portion of the sheet inside the mold has a developed surface equivalent to the surface of the fingerprint of the corresponding mold part; in this case the impression of the upper part (2), in the case illustrated. This avoids any defect of off-centering the cover sheet (8) relative to the rest of the structure that can be a major cause of rejection when the sheet is pre-decorated

  before the setting in mold, for example.

  After closing, the bracing pieces (6) can be slightly deformed by crushing and thus adapt to the variation in thickness of the cross section as a function of the length of the molded structure. It is thus possible to use only a limited series of parts of different thickness by providing for making each part in a deformable plastic semi-rigid material or

  metal made by injection or extrusion, for example.

  The bracing piece locally supports the cover sheet by bosses (63) for example, and thereby holds the local reinforcement members (7) in place at a predetermined distance from the lower surface of the sheet.

covering (8).

  The next step illustrated in FIG. 4 consists in injecting into the closed volume the constituents of a foam (9), of the polyurethane type for example, namely an isocyanate component and a polyol component which react 'in situ' causing a heat release and foam expansion. Sufficient injection of the constituents is provided for the foam (9) to fully fill the

defined volume.

  The foam thus fills the space between the lower plate (5) and the sliding sole (3) and the space between each local reinforcing element or rod (7) and the cover sheet (8). A homogeneous and highly cohesive structure is obtained in which the elements serving to reinforce the structure are trapped in the foam after hardening. The foam also repels and plates the cover sheet evenly against the walls of the upper mold. The sheet thus takes its final form in the mold. The forming of the sheet can be promoted by heating the mold at a temperature and for a sufficient time, depending on the nature of the material used. The material constituting the layer (s) of the cover sheet is chosen from the group of aliphatic polyamides, polyether block amide, polyether block ester, polycarbonates, ABS (Acrylonitrile Butadiene Styrene), AS (Acrylonitrile Styrene) pure or mixed with a TPU (thermoplastic urethane elastomer), polyethylene terephthalate (PET), polybutadiene terephthalate (PBT), polyurethane, polyolefin, as well as

  mixtures and copolymers of some of these constituents.

  Similarly, the local reinforcing elements or rods are made of material selected from the group consisting of: a metal of the steel, aluminum or aluminum alloy type, a reinforced plastic material. In the latter case, during the setting into mold, the rods are based on glass fibers, carbon or aramid and a

  thermosetting or thermoplastic resin matrix.

  Figure 5 illustrates, in cross section, the structure after injection of the foam and molding between two local parts spacer. Thanks to the bracing pieces, a predetermined distance (d) is ensured between each

  local reinforcing element (7) and the covering sheet (8).

  Figure 6 shows the longitudinal arrangement of the local reinforcing members (7) and the even distribution of the bracing pieces (6) along the molded structure. By way of example, the structure has the shape of a ski which schematically has a shape in wasp size. The width of each piece (6) may be variable to accommodate the variation in particular width of the ski. The local reinforcing members (7) extend longitudinally forming a bundle with high bending and torsional stiffening characteristics. These features can be easily modulated longitudinally and laterally by changing the number and / or length of the elements (7). It is possible, for example, to increase the mechanical characteristics of the ski in the central zone by adding several additional elements (7) of limited length.

in the area to be reinforced.

  According to a variant of the invention, the molded structure can be entirely reinforced by local elements or rods upper (70) and lower (71) as shown in Figure 7. In this case, the spacer part (6) comprises both a series of upper housing (620) and a series of lower housing (621). Through bosses (631) the spacer piece holds the lower rods (71) in place at a distance from the gliding sole (3) so as to allow the foam to circulate freely for perfect cohesion

of the structure.

  With the method according to the invention, reliefs (80) or recesses (81) can easily be obtained on the surface of the cover sheet (8). These shapes are formed by the deformation of the sheet (8) in contact with corresponding recesses or relief in the cavity of the mold and under the pressure exerted by the expansion of the foam during the injection step. In the case of Figure 8, the spacer piece (6) comprises upper housings (62) which are open towards the inside of the structure. The elastic compressibility of the workpiece is enhanced by tabs (64) that act as springs within the structure. The lower reinforcing member (50) is held in contact with the sole (3) by the tabs (64). It may be a plate of fibrous material pre-impregnated with an epoxy resin, for example. With heat, during injection molding, the crosslinking of the resin is obtained and

  simultaneously the gluing of the plate on the sole and with the foam.

  As shown in FIG. 9, the spacer piece (6) may also be a profile section having a series of holes (65) which extend substantially in the direction of the molded structure, and whose section transverse is slightly greater than the cross section of each upper reinforcing element (7). The prepositioning of the upper elements (7) is obtained by simply sliding in their hole of adapted section

corresponding.

  Of course, the molded structure is not limited to the examples described and one can imagine other structures without departing from the scope of the present invention. FIG. 10 thus illustrates another variant in which the lateral reinforcement can be increased by a edge element (82) positioned on each lateral edge (4) and extending over a large part thereof. The cover sheet forms only part of the edge of the molded structure,

  whose lateral edges rest on each edge element (82).

  In the process described, the forming of the cover sheet is carried out by the foam itself. It may be otherwise in the case where, for example, the material used for the sheet is not easily deformable or when the final shape to be achieved is relatively complex. In this case, it may be necessary to apply a step of preforming the upper cover sheet,

  prior to the molding step.

Claims (12)

  1- A method of manufacturing a molded structure having the shape of an elongated beam consisting; - To have in a mold a lower subassembly comprising a sliding sole (3) bordered on either side by lateral edges (4) optionally a lower reinforcement element (5, 50); - Covering the lower subset of a cover sheet (8), to form a closed volume, intended to form the top and at least part of the side faces of said structure; - to close the mold; then injecting into the volume thus defined the reagents of a foam (9) which expands 'in situ'; - Then to open the mold to remove the complex molded structure, characterized in that at the time of setting into mold, there is intercalated between said lower subset (3, 4, 5, 50) and said cover sheet (8), a plurality of local bracing pieces (6) longitudinally distributed over at least a portion of the length of the molded structure; said pieces being spaced apart from each other, resting on the lower subassembly and holding in place a plurality of local reinforcing members (7, 70, 71) of small width, spaced apart   laterally to one another across the width of said molding structure.   2- A method of manufacturing a molded structure according to claim 1, characterized in that the bracing pieces (6) locally support the cover sheet (8); and holding in place local reinforcing members (7, 70) at a predetermined distance from the bottom surface of said cover sheet (8) to promote passage of the foam (9) between   reinforcement elements (7, 70) and said cover sheet (8).   3- A method of manufacturing a molded structure according to claim 1 or 2, characterized in that the bracing pieces (6) are obtained from one or more plastic or metal profiles made by injection , by   extrusion or pultrusion, then cut into sections of determined length.   4- Process for manufacturing a molded structure according to any one of   preceding claims, characterized in that each bracing piece   (6) is a section of flattened tube whose wall comprises, at least, a series of open recesses (62, 620, 621) of concave cross-section and which extend substantially in the longitudinal direction of the structure molded   in which are inserted the local reinforcing elements (7, 70, 71).   - A method of manufacturing a molded structure according to claim 4, characterized in that the cross section of each housing (62, 620, 621) comprises a narrowing zone to allow engagement by clipping   of each top element of local reinforcements.   The method of manufacturing a molded structure according to claim 1, 2 or 3, characterized in that each bracing piece (6) is in the form of a profile section having a series of holes (65) which extend substantially in the longitudinal direction of the molded structure, and whose cross-section is slightly greater than the cross-sectional area of each local reinforcing element (7). 7- A process for producing a molded structure according to any one of   preceding claims, characterized in that the bracing pieces (6)   are made of a deformable semi-rigid material to adapt to the variation in thickness of the cross section as a function of the length of the molded structure.   8- A method of manufacturing a molded structure according to any one of   Claims 1 to 6, characterized in that the bracing pieces (6) are   made of a rigid material resistant to crushing.   9- Process for manufacturing a molded structure according to any one of   preceding claims, characterized in that the local reinforcing elements   (7, 70, 71) are circular, oval or polygonal full section rods.   10- A method of manufacturing a molded structure according to claim 9, characterized in that the rods are made of material selected from the group consisting of a metal type steel, aluminum or aluminum alloy, a reinforced plastic material.   11- A method of manufacturing a molded structure according to claim 10, characterized in that during molding, the rods are based on glass fibers, carbon or aramid and a thermosetting or thermoplastic resin matrix. 12- A method of manufacturing a molded structure according to any one of   preceding claims, characterized in that a step of   preforming the upper cover sheet (8) prior to the step of setting in mold.   13- A method of manufacturing a molded structure according to any one of   preceding claims, characterized in that upon closure of the mold,   the side edges of the cover sheet are firmly gripped in the air gap in the vicinity of the joint plane (100) of the mold; without the possibility of slipping, and in that it is expected that the part of the sheet inside the mold has a developed surface equivalent to the surface of the mold.   the impression of the corresponding part of the mold.   14- A method of manufacturing a molded structure according to any one of   preceding claims, characterized in that the cover sheet (8)   comprises a single layer or several pre-assembled plastic layers. 15- A method of manufacturing a molded structure according to claim 14, characterized in that the material constituting the layer (s) of the cover sheet is selected from the group of aliphatic polyamides, polyether block amide, polyether block ester, polycarbonates, ABS (Acrylonitrile Butadiene Styrene), AS (Acrylonitrile Styrene) pure or blended with TPU (thermoplastic urethane elastomer), polyethylene terephthalate (PET), polybutadiene terephthalate (PBT), polyurethane, polyolefin , as well as   mixtures and copolymers of some of these constituents.   16- A method of manufacturing a ski according to any one of claims 1   to 15. 17- A method of manufacturing a snowboard according to any one of Claims 1 to 15.