FR2717558A1 - Structural element and its manufacturing process. - Google Patents

Abstract

Structural element comprising a structural element with hollow section (10) of a first material and whose inherent rigidity (stiffness) has been improved by the introduction, inside the cavity (11) of the hollow section, of a elongated body substantially the same length as the structural element, said elongated body filling all or part of said cavity and comprising a second material of density lower than that of the first material, and said elongated body further comprising at least one reinforcing element (12, 13, 14) substantially the same length as the structural element and made of a third material and which is linked to said second material.

Description

STRUCTURAL ELEMENT AND MANUFACTURING METHOD THEREOF.

  The present invention relates to structural elements, and also to the

  process for manufacturing these structural elements.

  Hollow structural elements produced by extrusion are very widely used; these can be made of aluminum or plastic. The profiles are

  usually made at lengths up to 5 or 6 meters.

  These structural elements are widely used in the construction of greenhouses, for example. When used as glazing supports (standard length in the range of only 2.8 to 3.0 m) for the roof of a greenhouse, bending down the glazing support is often unacceptable by following (a) the length of the support and (b) the weight of the glazing (the latter may be made of glass, or, for example, of polycarbonate), said weight constituting a considerable problem when elements with double glazing are used. Snowfall, wind and downward pulls aggravate this fact. In addition, in other buildings, these structural elements are used as constituents of vertical walls where the effect of the wind can cause inward or outward bending of mullions and lintels depending on the direction. the wind

  relative to the particular face of the building comprising said vertical wall.

  In addition, in the field of domestic and industrial buildings, the roofs include trusses which themselves include rafters; rafters used to support the weight of tiles or other roofing materials. The rafters can, over time, bend under the weight of the roofing material only and, even more, during a

2 2717558

  snowfall or when wind pressure is exerted on the roof periodically

  for several years. The rafters can be torn off.

  The problem of unacceptably bending bars due to the inherent rigidity (stiffness) of the extruded lengths of the aforementioned materials is not sufficiently high, and the main object of the present invention is to attempt to increase the

  rigidity (stiffness) of the structural elements without unacceptable increase in their weight.

  According to the present invention, a structural element comprises a hollow structural element made of a first material and whose inherent rigidity (stiffness) has been improved by the inclusion, inside the cavity of the hollow section, of an elongated body. substantially the same length as the structural element, said elongated element filling all or part of said cavity and comprising a second material of density lower than that of the first material, and said elongated element further comprising at least one reinforcing element which is substantially the same length as the element

  structural and which is made of a third material and secured to said second material.

  The structural element may be straight or may have a curvature.

  The second material can be a plastic in the form of foam; for example polyvinyl chloride, polyurethane or styrene, and may be of the type which becomes foam as a result of the action of humidity in the ambient air or

  result of the interaction of the constituents of a two-component chemical mixture.

  Other suitable materials can be used such as (a) wood chips (or sawdust) joined together by an adhesive and (b) wood chips (or sawdust) more

cement / concrete and aerated.

  The reinforcing element can be, for example, made of metal or carbon fibers and preferably has a high elastic modulus for the material concerned, so for aluminum the modulus would typically be 70 G.Pa and for l steel typically

  204 G. Pa, an appropriate value being used for other materials.

  Four reinforcing elements may be provided, each of which is of angular section, the elongated body having the sectional shape of a rectangle and said reinforcing elements being located at or near the vertices of the rectangle of the body. In another embodiment, two L-shaped reinforcing elements can be used, arranged in relation to each other to form, in section, a rectangular shape whose sides are parallel to the walls delimiting the cavity of the 'structural element. In other modes of

3 2717558

  embodiment, at least a pair of reinforcing elements in the form of a strip can be arranged at or near an opposite pair of faces on the interior walls of said

hollow section element.

  The present invention also encompasses a structural member as set out above which is supported in one or more directions along its length. The elongated body can be a preformed element which is introduced into said cavity. As a variant, said elongated element can be linked to the structural element at the

  following an in situ treatment in the cavity.

  The present invention also comprises a method of manufacturing a structural element comprising filling all or part of a hollow section structural element made of a first material with an elongated body substantially of the same length as the sectional structural element hollow and in a second material of lower density than the first material, and the incorporation in said elongated element of a reinforcement element substantially of the same length as the elongated body and made of a third material, and the connection of said reinforcement element second material audit. Thus, the method may include the steps of extruding a hollow member, preforming said elongated body with a sectional surface which is substantially the same as a cavity in said hollow section member and incorporating at least one reinforcing member to the interior, and the introduction of said elongated body into said cavity of said hollow section member. Another implementation method of the invention comprises the steps consisting in extruding a hollow section element and creating inside a cavity in said hollow section element an elongated body to substantially fill said cavity and in

provide a reinforcing element.

  Another object of the present invention is to solve the problem presented

  in the introductory paragraphs in a different way from those already suggested.

  Thus, instead of trying to improve the inherent rigidity (stiffness) of an already existing hollow section structural element which may, for example, have been purchased from a supplier

  of these structural elements and fabricate a structural element from the start.

  Thus, the process can include the steps of: (1) feeding continuously and simultaneously into an extrusion head;

4 2717558

  (a) a heated plastic (b) at least one reinforcing element, and (c) another material whose density is lower than that of the plastic and the reinforcing element; (2) extruding said plastic material to form a structural element with a hollow section inside the cavity of which the or each reinforcing element is placed; (3) cooling the profile by means of a cooling jacket which constitutes a part of the extrusion head; and (4) then introducing said other material, the density of which is lower than that of the plastic material and of the or each reinforcing element in the cavity in order to fill the latter and to bind it both to the plastic material or to to each reinforcing element. The method also includes bending or forming the hollow section structural member to form one or more curves in one or more

  directions along its length before filling with said elongated body.

  Exemplary embodiments of a structural element with a hollow section according to the present invention, and of a method for manufacturing such an element, will now be described by way of example and with reference to the appended schematic drawings in which: Figure 1 shows a section through a typical structural element of extruded material (eg PVC) with a U-shaped reinforcement element placed in its cavity Figure 2 represents the ideal positioning inside the cavity of an element structural, which is the same as that shown in Figure 1, of four reinforcing elements; Figure 3 shows the same section as Figure 2 but after injection of a plastic material in the form of foam; Figure 4 shows schematically a split mold for the manufacture of an elongated preformed body; Figure 5 shows the preformed body after removal of the split mold; Figure 6 shows the same typical structural element of extruded PVC as above and in the cavity of which are placed two reinforcing elements;

2717558 -

  Figures 7 to 8 show in elevation and in section, respectively, one of the reinforcing elements shown in Figure 6; FIG. 9 represents a way in which two reinforcing elements can be arranged inside the cavity of a structural element by a spacer before the injection of the plastic material in the form of foam into the cavity; Figure 10 shows a side elevation of such a spacer, outside the structural element, with the two reinforcing elements applied; Figure 11 shows the same typical structural element as above, this time reinforced in separate planes X-X and Y-Y by incorporated reinforcing elements arranged in pairs; Figure 12 schematically shows a structural element supported from below before injection of the plastic material in the form of foam; Figure 13 shows the same type of structural element as shown in Figure 12, but subjected to an upward force and two downward forces; Figure 14 is a schematic representation of a device for manufacturing a structural element according to the invention; and

  Figure 15 is a sectional view along line XV-XV of Figure 14.

  Figure 1 shows a structural element according to the invention which comprises a hollow-section structural element in the form of a profile 10 (for example, made of PVC) for use as a glazing support element or other structural element of hollow section and has a main cavity 11 (other small cavities, if they exist, being ignored). In order to reinforce the profile 10, an elongated body is produced in the following manner: A reinforcing element 12 produced in a suitable U-shaped section is positioned in the cavity 11 in the position shown; the reinforcing element 12 consists of parallel elements 13, 14 and a connecting piece 15 which keeps the elements 13, 14 spaced apart. When the reinforcing element 12 is positioned, a plastic material in the form of foam (not shown) is injected into the cavity 11 in order to fill the latter and create said elongated body. The plastic material in the form of foam is linked to the profile 10 and to the reinforcing element 12. Thus, the foam constitutes a second material of density lower than that of the first material of the profile 10 and the reinforcing element 12 made of metal , for example aluminum or steel, or plastic

6 2717558

  reinforced with carbon fibers (RCP), is a third material. The reinforcing element is arranged to have a high modulus of elasticity, which is for example, in the case of aluminum, typically 70 G. Pa or in the case of steel, typically

  204 G. Pa, and an appropriate value for other materials.

  The inherent stiffness or rigidity of the profile 10, which can be 3 m in length or more, is greatly increased by the elongated body which includes the element of

  reinforcement 12 and the plastic in the form of foam.

  Figure 2 shows a profile 20 having a cavity 21 in which are arranged four reinforcing elements 22 in the positions shown, a plastic material in the form of foam 23 (Figure 3) is injected into the cavity so as to fill it and thus create an elongated body comprising the elements 22 and the plastic material in the form of foam 23. The plastic material in the form of foam surrounds some of the elements 22 or pushes all or some of these into the adjacent peaks of the

profile 20.

  The reinforcing elements 22 are supported by a succession of spacers (not shown in Figures 2 and 3), the role of which is to allow the desired lengths of reinforcing elements to be introduced into the profile in their appropriate positions in which they will be maintained before the foam injection. The

  spacers can be placed for example, at intervals of lm or 0.5m.

  Figure 4 shows, in schematic form, a split mold 30 in which four reinforcing elements 31 have been arranged using a series of spacers (not shown) for the same purpose as described above. The mold 30 is then closed and a plastic material in the form of foam is injected into the mold with the result that said material, designated by the reference numeral 32, either surrounds some of the elements 31, or pushes all or some of it. them in the adjacent vertices of the

mold 30.

  The resulting product, when removed from the mold 30, is an elongated preformed body 33 (Figure 5) which has four reinforcing elements 31 which have been incorporated into and bonded to the plastic in the form of foam 32. The product is made to the same length as that of the profile to be reinforced, and is introduced into the cavity of said profile (for example, a cavity similar to the cavity 11 of the profile 10). The product is produced in a mold so as to ensure that the product has a cross-sectional shape and

7 2717558

  a sectional surface which is the same as that of the profile cavity to be reinforced. Figure 6 shows a profile 40 having a cavity 41 in which are positioned two reinforcing elements 42. Each reinforcing element 42 is in the form shown in Figures 7 and 8, namely, an approximate shape of L in section and having perforations 43 in branch 44 thereof. The plastic in the form of foam, after injection, will completely surround the branches 44 of the elements 42 through the perforations 43. The perforations 43 ensure the lightness of the elements 42 and also allow satisfactory integration of said elements with the plastic material in the form of foam. The same applies if the reinforcing elements 42

  are placed in a split mold of the type shown in Figure 4.

  Figure 9 shows a profile 50 having a cavity in which are arranged two reinforcing elements 51; said elements are supported by a succession of spacers 52 (see also Figure 10) which are placed at 0.5 m intervals along the elements 51. The spacers 52, which can be molded or manufactured differently at low cost, ensure that the separate reinforcing elements 51 are held approximately in their desired final positions. Each spacer 52 has a large opening 53 so that the foam-like plastic can flow

  freely through the cavity and create an elongated body.

  Figure 11 shows a profile 60 having a cavity in which are placed four reinforcing elements 61, 62, 63, 64, said elements having been incorporated (in situ or in a split mold) in the plastic material in the form of foam 65 for create an elongated body. Pairs of reinforcing elements on opposite sides of the body

  elongated reinforce the profile in two different planes X-X and Y-Y.

  Figure 12 shows a profile 70 which is supported on a flat surface before injection of a plastic material in the form of foam in its cavity 71. If reinforcing elements have been placed in the cavity as described above with reference in Figures 1 to 3 and 6 to 11 before foam injection, the reinforced profile will be

  (after foam injection) a reinforced straight profile.

  The structural element can however be made with one or more

curvatures along its length.

8 2717558

  For certain applications, however, it can be considerably advantageous for the reinforced profile to have a curvature in order to be able to withstand a high load; if any load exerted on a reinforced profile which is bent upwards is such that a downward deviation of the profile occurs, this deviation would only result in the reinforced profile bent upwards by a straight reinforced profile ( or slightly less curved). This is shown, very exaggerated, in Figure 13 in which a profile 80 is subjected to an upward force F2 at or near its midpoint and to downward forces F1 at or near its ends. If the previously curved profile (which already preferably has inside its cavity a known arrangement or formed of reinforcing elements as described above with reference, for example, either in Figure 2 or Figures 9/10) and with a plastic material in the form of foam injected into its cavity to create an elongated body, the profile 80 retains its curvature (completely or partially) when the forces are removed. A variant of obtaining the same effect is to manufacture, using an appropriately curved split mold, a product similar to that shown in FIG. 5 but curved longitudinally; a product thus curved is then slid into the previously curved profile and said profile retains its curvature (completely or partially) when the

  forces that created the curvature of the unreinforced profile are eliminated.

  Referring to the previous paragraph and to the explanation of Figure 13 in particular, it should be emphasized that almost any predetermined curvature can be caused by changing the number and amplitude (and points

  of application) of the forces exerted on the profile.

  Figure 14 shows the structure of an extrusion head for a mold that

  can be conveniently used to manufacture a structural element according to the invention.

  The extrusion head 100 is supplied with molten plastic material 101 which is continuously supplied under pressure. The plastic molded under pressure escapes via an opening 102 and, in the case of a hollow profile 103,

  this is made between the face 104 of the extrusion head and a bridge element 105.

  Simultaneously with the extrusion of the molten plastic 101 from the shaped opening 102, reinforcing elements 106 are continuously delivered through the head and through the opening 102 simultaneously with the extruded plastic. The

9 2717558

  reinforcing elements 106 are internally guided (not shown) so that they

  line the interiors of the faces of the extruded walls 107 of the profile 103.

  When the combination of the semi-molten profile 103 and the reinforcing elements 106 progresses through and out of the extrusion head 100, it passes through one or more cooling stations designated by the reference numeral 108 (only one station

being shown).

  At a suitable point inside the profile 103 after solidification of the plastic material, the liquid material 109 is injected under pressure into the center of the profile 103, via a supply tube 110 extending directly to i0 through the extrusion head 100. This liquid changes state to become a core in the form of foam 111 at a more distant point along the combination of reinforcement foam.

  profiled, this point being represented by the reference number 112.

  Figure 15 shows a section through the finished material which includes an outer wall of rigid plastic 107 containing reinforcements 106 (two being shown) and cured foam 111 secured to form a homogeneous whole. It will be noted that the reinforcements 106 are delivered via

  sealing means 113 arranged in the wall of the extrusion head 100.

  Although glazing profiles have been described above, it will be understood that other elements, for example mullions, lintels and rafters or other structural elements can be produced according to the present invention, that these structural elements support glazing or whatever, and these structural elements are

extruded or molded.

  Although the aforementioned structures make use of a plastic material in the form of foam for the creation of the elongated body, other materials (for example, wood chips / sawdust joined together by a glue, or aerated wood chips / sawdust more

  glue / concrete already mentioned) can be used to give satisfactory results.

  In addition, as used in the present description, the word "curved" includes

  not only what is shown and given as an example in Figure 13, but also what is not shown and which consists of three or more straight parts joined together (a Mansard roof is a well known example of a curved roof which, as seen in section, consists of three rectilinear roof parts joined together). The fact of giving a curvature to structural elements in order to make it curved (as defined above) is important for these elements which are placed horizontally and not only for those

  which are placed other than horizontally.

  Some of the advantages obtained by the implementation of the present invention are: for greenhouses, (a) the invention allows the use of the entire length of an extruded glazing bar which, when it is reinforced in the traditional way , would "bend" unacceptably under the action of its own weight; (b) the present invention provides a glazing bar substantially lighter than the conventional method, thus facilitating adjustment and machining; (c) the invention allows the use of hermetic glass units with greater spans, thanks to the prestressing of the glazing bar to compensate for the weight of the glass unit, thus, when the hermetic unit is fixed in the glazing bars, the appearance of the roof is level looking forward and backward, whatever the pitch to which the roof is fixed (for example 10 or 30); (d) at least when a plastic material in the form of foam is used, the foam which binds the reinforcing elements to the profile has excellent insulation qualities, thereby improving the "u" value of greenhouse roofs and in that concerned

especially condensation.

  For a vertical wall, now, the support of a vertical pvc wall system requires a large substructure of steel, but the reinforcement of pvc mullions according to the present invention not only provides better deflection properties, but also better insulating properties, due to the fact that there is

  no steel from front to back.

Claims (30)

  1. Structural element, characterized in that it comprises a hollow-section structural element (10; 107; 20; 40; 50; 60; 70; 80) made of a first material and whose inherent rigidity (stiffness) has been improved by the inclusion, inside the cavity (11; 21; 41; 71) of the hollow section, of an elongated body (111; 23; 32) substantially the same length as the structural element, said elongated body filling all or part of said cavity and comprising a second material of density lower than that of the first material, and said elongated body further comprising at least one reinforcing element (12, 13, 14; 106; 22; 31; 42; 51; 61, 62, 63, 64) which is substantially the same length as the structural element and which is made of a third material and which is linked to said second material.   2. Structural element according to claim 1, characterized in that said   second material is plastic in the form of foam.   3. Structural element according to claim 2, characterized in that said plastic material in the form of foam is polyvinyl chloride, polyurethane or styrene.   4. Structural element according to claim 2 or claim 3, characterized in that said plastic material is of the type transforming into foam as a result of the action of humidity in the ambient air or as a result of the interaction of   components of a two-component chemical mixture.   5. Structural element according to any one of claims 2, 3 or 4,   characterized in that said reinforcing element is incorporated in and linked to said material plastic in the form of foam.   6. Structural element according to claim 1, characterized in that said second material is wood shavings or sawdust bonded by an adhesive or shavings   wood or sawdust plus glue / concrete and airy.   7. Structural element according to any one of the claims   above, characterized in that said reinforcing element is made of metal or fibers of carbon.   8. Structural element according to claim 7, characterized in that said reinforcing element has a high modulus of elasticity for the material concerned.   9. Structural element according to any one of claims   previous, characterized in that it comprises four reinforcing elements (22; 31) of which each is of angular section.   10. Structural element according to claim 9, characterized in that said elongated body has a rectangular cross-sectional surface, said reinforcing elements being   located at or near the vertices of the body rectangle.   11. Structural element according to any one of claims 1 to 8,   characterized in that it comprises two L-shaped reinforcing elements (42) which are arranged to form in section a rectangle whose sides are parallel to the walls   defining said cavity of the structural element.   12. Structural element according to any one of claims 1 to 8,   characterized in that it comprises a pair of reinforcing elements in the form of a strip (106; 51) which are arranged at or near an opposite pair of faces on the walls   interior of said hollow section member.   13. Structural element according to any one of claims   above, characterized in that said elongated body is a preformed unit which has been introduced into said cavity.   14. Structural element according to any one of claims 1 to 11,   characterized in that said elongated body is linked to the structural element following the   in situ formation in said cavity.   15. Structural element according to any one of claims   above, characterized in that it is supported in one or more directions along its length. 16. Method for manufacturing a structural element, characterized in that it comprises filling all or part of a structural element with hollow section made of a first material with an elongated body substantially the same length as the element structural hollow section and a second material of lower density than the first material, and the incorporation in said elongated body of a reinforcing member substantially the same length as the elongated body and consisting of a third   material, and the connection of said reinforcing element to said second material.   17. The method of claim 16, characterized in that it comprises the extrusion of a hollow element, the preforming of said elongated body with a sectional surface substantially identical to that of a cavity in said element with hollow section and l incorporation of at least one internal reinforcing element, and the introduction of said body   elongated in said cavity of said hollow section member.   18. The method of claim 16, characterized in that it comprises the steps consisting in extruding a hollow section element and in creating inside an cavity of said hollow section element an elongated body to substantially fill said cavity and   the provision of a reinforcing element.   19. The method of claim 16, characterized in that it comprises the steps consisting in (1) continuously and simultaneously delivering into a extrusion head (a) a heated plastic material (b) at least one reinforcing element, and (c) another material whose density is less than that of the plastic and the reinforcing member; (2) extruding said plastic material to form a structural element with a hollow section inside the cavity of which the or each reinforcing element is disposed; (3) cooling the profile by means of a cooling jacket which is part of the extrusion head; and (4) then introducing said other material whose density is lower than that of the plastic and of or each reinforcing element into the cavity in order to fill said cavity and to secure it both to the plastic and to or every reinforcing element.   20. Method according to any one of claims 15 to 18, characterized   in that it includes the use of a plastic in the form of foam as says second material.   21. The method of claim 20, characterized in that said plastic material in the form of foam is polyvinyl chloride, polyurethane or styrene. 22. The method of claim 20, characterized in that it comprises the use of wood shavings or sawdust bound by an adhesive or wood shavings or   sawdust plus cement / concrete and airy.   23. Method according to any one of claims 16 to 22, characterized   in that said reinforcing element is made of metal or carbon fibers. 24. The method of claim 23, characterized in that said element of   reinforcement has a high elastic modulus for the material concerned.   25. Method according to any one of claims 16 to 24, characterized   in that four reinforcing elements are provided, arranged so as to be located at or near the vertices of the rectangle of the cavity of the element of hollow section, cavity which is rectangular in section.   26. Method according to any one of claims 16 to 24, characterized   in that two L-shaped reinforcing elements are provided which are arranged to form in section a rectangle whose sides are parallel to the walls delimiting said structural element cavity.   27. Method according to any one of claims 16 to 24, characterized   in that a pair of strip-like reinforcing elements are provided which are arranged at or near an opposite pair of faces on the inner walls of said element hollow section.   28. Method according to any one of the preceding claims,   characterized in that it includes bending or forming the hollow section structural element to form one or more curves in one or more directions along its length   before filling with said elongated body.   29. The method of claim 28, characterized in that it comprises bending the structural element in a curve or curves by applying forces   appropriate and then filling with said elongated body.   30. The method of claim 29, characterized in that said bending forces are applied with the one or more reinforcing elements in position before the   filling with said elongated body.