FR2540037A1 - PROCESS FOR MANUFACTURING A COMPOSITE WORKPIECE OF ALVEOLARY SYNTHETIC MATERIAL AND OBTAINED PIECES - Google Patents

Abstract

at. A method of manufacturing a piece of cellular synthetic material, such as polystyrene, by injection molding. b. Process characterized in that during a first step, a blank 15 is produced in a first mold using a material of a first type, then, during a second phase, this is transferred. blank 15 in a manufacturing mold 19 which is filled 18 with a second material. According to a variant the two materials are the same, but with different densities. vs. The invention relates to the manufacture of cellular parts especially intended for construction, building, packaging for technical parts intended for the automobile and various industries. (CF DRAWING IN BOPI)

Description

"Process for manufacturing a piece of synthetic material

alveolar and obtained parts ".

  The present invention relates to a manufacturing process

  cation of a piece of cellular or expanded synthetic material such as polystyrene by injection molding as well as

the pieces obtained.

  The multiple advantages of expanded plastics such as polystyrene, have led to a significant development of the use of this material for the manufacture of the most different parts using the characteristics of insulation, stiffness

and lightness of this material.

  Thus, an important area of use

  such expanded materials is the building for the manufacture of

  interframe, inter alia, expanded polystyrene, or the manufacture of wedging elements used for packaging fragile products, such as household electronic equipment (television, radio receiver, string

HIFI, etc).

  Depending on the strength that the piece must exhibit, the density of the polystyrene is modified during the

injection molding.

  Thus, for the realization of interstices expanded polystyrene, we must take into account a specification that the slabs thus produced can withstand a load of 150 da N, which requires the production of parts having a density of However, in spite of this, the spoilers of interjoists constitute the most fragile element. It is therefore necessary that, taking into account the thickness and the structure of these spoilers, the density of the whole product either

  chosen for these spoilers to withstand the expected loads.

  However, the increase in the cost of raw materials and fuel (necessary for injection molding), result in a relatively high cost.

  products, putting into question its competitiveness.

  Problems of the same nature arise for parts used substantially under similar conditions, such as, for example, wedges used for electronic devices. These wedges are in the form of rings or flanges of rectangular section, which surround the parallelepiped box. of the electronic device, to ensure its positioning in the cardboard box and allow the stacking of the boots. In general, parts of the above type have a certain shape, but only certain parts of the part must have adequate strength, the other parts constituting

  than the necessary filling of the volume.

  This results in a loss of material and

manufacturing cost.

  The object of the present invention is to create a process for manufacturing expanded plastic parts, in particular made of polystyrene by injection molding, which makes it possible to save a considerable amount of material and weight without reducing the strength characteristics of the product produced, by adapting the product structure to

his function.

  To this end, the invention relates to a method * characterized in that, during a first step, a blank of a first part of the part is produced by filling a first mold cavity using of a material of a first type and then during a second phase, this blank is transferred into a manufacturing mold to perform the filling normally around or against the blank with a material of a second type then it is followed to all so realized, the normal cycle of manufacture. According to an interesting characteristic, the two materials are materials of the same type

but of different density.

  According to another characteristic, when

  the invention is applied to a production cycle

  a hot mold and a cold mold (Ritter process),

  the blank is placed in the hot mold.

  The process according to the invention offers considerable advantages both in the production and in the diffusion and

  to the use of the pieces thus produced.

  Indeed, the process is totally different from the manufacturing process of molding a part with inserts because the inserts are made in a separate process and do not constitute blanks

parts parts.

  The inserts currently used are from parts whose injection is complete, that is to say of which

  the heat treatment is finished and these parts are-

to definitive dimensions.

  In contrast to this, the method according to the invention consists in producing successive blanks of parts of the part-then when all the blanks are made, to perform the final heat treatment (cooking), treatment during which the piece is put -in definitive dimensions During this final phase, all the blanks are cooked at the temperature

  and are expanded, which ensures the

  penetration of the junction surfaces of the different blanks and consequently an excellent solidarity of the parts (blanks) between them increasing the mechanical strength of the assembly Such a bonding by interlocking the contact surfaces, by local deformation of these surfaces, interpenetration by the balls expanded material, etc., is not possible in the case of inserts since they are necessarily finished parts Moreover, this is even necessary because the blanks would not have the necessary resistance

  handling, storage and transport.

  The invention also relates to the products

  obtained by the implementation of the method.

  These products or molded parts in several stages have interesting features related

  to the shape of the different parts of reinforcement.

  According to a first feature, the part consists of interjoists comprising reinforcing elements selected from the group formed by a vault, a structure with angles and cross members, lateral angles, these reinforcing elements being made of a material which is stronger than the material

  wherein these elements are partially embedded.

  According to another characteristic, the part is constituted by a wedge for apparatus, in particular household appliances, comprising reinforcing elements chosen from the group formed by wedges, spars, crosses, plates made of a material more resistant than the material in which these items

are at least partially embedded.

  According to another characteristic, the piece is constituted mar a box, fish crate, fruit crate, at least partially provided with a reinforcement surround in

  a stronger material than the other parts of the box.

  According to another characteristic, the material constituting the reinforcing elements is the same as that constituting the other parts of the piece but

its density is stronger.

  The present invention will be described in more detail with the aid of the accompanying drawings in which: FIG. 1 is a diagram of an expanded polystyrene interjoists placed on two beams, FIGS. 2A and 2B respectively show a view of cut, a perspective view of a hold

for household appliances.

  FIGS. 3A and 3B are two sectional views of a slab and a wedge, according to the invention. FIGS. 4A and 4B represent the two main steps of the product manufacturing process, according to the invention FIGS. 5 to 13 are perspective views of different products according to the invention, the reinforcing parts being represented in solid lines and in grisaille, and the outline of the parts

in fine lines.

  According to FIG. 1, the known interjoist 1 made of expanded polystyrene has two lateral spoilers 2 through which the interjoists 1 rests on the flanges of the beams 3. FIG.

  break 4 possible at each spoiler 2.

  To avoid this break, it is necessary to produce the expanded polystyrene slab 1, with a relatively high density of the order of 25 to 30 gr / l to meet the load conditions to which

  must theoretically resist this interview.

  FIGS. 2A and 2B show a wedge 5 in the form of a rectangular ring provided with an opening 6 whose shape, for example rectangular, is adapted to that of the casing of the apparatus to be packaged. The wedge 5 is put in place on the as shown in FIG. 2B. In these conditions, only the part to the right of the apparatus, that is to say of the opening 6 in each of the four

  directions, must withstand the weight of the device and the

  seems to hold 5-must withstand the weight of several

  appliances stacked one above the other.

  However, if this wedge 5 was made with a low density, the relatively large volume of the wedge would allow it to withstand the load resulting from the stacking of several products but the very high local stresses which are exerted on the level of the window 6 could not be transmitted by a low density polystyrene So is it necessary to increase the overall density of the product, that is to say to go from a density of 15 gr / l to for example a density of

gr / l.

  Figures 3 A and 3 B schematically show a interjoists and a wedging piece manufactured according to the invention. The interjoists 10 in FIG. 3A consist of an inner reinforcing portion 11 surrounded by a portion 12 giving the appropriate overall shape but

  having only a very small support function.

  The packing shim 12 ', according to FIG. 3B,

  consists of a reinforced part 13 and an outer part

  This assumes that the orientation of the part is not arbitrary and that the reinforced part 13 still serves as a support for the object to be packaged (that is to say

  part 13-is below the corresponding part of

from the room).

  The manufacturing process of parts such as those given by way of examples in FIGS. 3A and 3B will be described below with reference to FIGS. 4A-4B. FIG. 4A shows a first step of the process. of this first step, the filling of the blank 15 corresponding to a part of the part is carried out. This filling is done by injection of a

  first type of material in the cavity 16 of the mold 17.

  Then this material thus injected is partially cooked (that is to say temperature rise sufficient to ensure the setting and its holding in form of the material to

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  the interior of the molding cavity 16) This shaping is however not pushed to the final limit. According to FIG. 4B, during a following step (for example the second and only subsequent step), the preform 15 produced is transferred and deposited as indicated above into the cavity 18 of the mold 19, and then the material corresponds to for example to a second type to form the second part of the piece, and is injected

  in the cavity 18 around the blank.

  After the final filling of the cavity 18, the part is filled with two different materials, and the normal manufacturing cycle can be started (cooking,

  expansion, cooling and ejection).

  It suffices to multiply the number of blanks 15 so that ultimately the mold making the piece is filled with as many different materials as there are blanks, plus one, which is the filling material.

definitive of the cavity 18.

  According to the method described above, the material used to achieve the final filling of the second part of the part-in the cavity 18 may be the same material or a different material from that

used for roughing 15.

  In general, since the blank 15 is intended to form the reinforcement of the part, its strength must be greater than that of the other parts of the part so its density must be stronger than that of the other parts of the part. For this purpose, when the roughing is carried out, a high density blank, which is suitable, is formed, whereas for the filling of the second part or of the following parts,

  a lower density, in gradation for successive sketches -

  sive or varying according to a specific order.

  It is essential that the molding operations carried out in the phases preceding the final phase are at least partially pre-molding operations, that is to say giving a blank and not a product.

having its final form.

  This blank or the successive blanks must be strong enough to be transferred and deposited in the mold making the final piece.

  and that the draft is not destroyed during the operation

  Final filling ration of the piece.

  To improve the strength of the manufactured product

  as well as the mechanical strength not only of

  rents parts of the room, but also of the entire room, it is important that the different blanks are secured to one another at their intermediate surface (that is to say the following surfaces which

  the blanks are in contact with each other).

  This connection between the different parts of the part is carried out during the molding operation of the part which consists in cooking at the final temperature of the steam <in the case of an expanded material,

such as polystyrene).

  Different unrepresented installations can

  used for the implementation of the process according to the

  vention and these installations do not require other trans-

  formations as the modification of the molds.

  The method according to the invention can be used on traditional machines In the case of a two-part part, according to the invention, the traditional molding consists of two molds, one for the first blank, the other for the final shape These molds are as is known alternately heated and then cooled for

demolding.

  The method according to the invention can also be used on a hot and cold mold machine developed in recent years In this case, the filling

  definitive is done in the hot mold.

  Finally, the method can be implemented on so-called "process" machines, that is to say machines which comprise

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  means for making a partial vacuum inside the molds to accelerate the cooling of parts and reduce the working cycle Indeed, this method has no influence on the molding process. Figures 5 to 13 are perspective views of different parts, according to the invention, in which the reinforcing elements are represented with dark lines and the faces of these elements are in grisaille while the apparent outline of the complete parts

is represented in fine lines.

  Figure 5 shows a first mode of

  This interjoists 30 comprises a reinforcing arch 31 provided with lightening holes 32. This arch 31 is sandwiched between the upper part 33 and the lower part 34. This lower part 34 is extended by one side (right according to FIG. 5) by a plate 35 intended to cover from below

  the beam (not shown) that receives the interjoists.

  This extension 35 is necessary to ensure both

  insulation and continuity of the ceiling.

  FIG. 6 shows a second embodiment of an interjoists 40, according to the invention. This second mode is distinguished from the embodiment of FIG. 5 by the reinforcing element 41 in the form of a grid comprising

  lateral angles 42 and transverse elements 43.

  This structure is chosen to lighten the reinforcing element 41 without affaiklir Within the outline of this interjoists 40, the volumes and cavities other than those occupied by the reinforcing element 41, are occupied by a density material. weaker assuring

  simply the shape of the whole and the filling.

  Figure 7 shows a third mode of

  This interjoists, the outer shape of which is similar to that of the two previous embodiments, comprises two reinforcing spars 51 along the lateral edges, to reinforce the most fragile part of the interjoists at the end. level of the spoilers by which it is supported on the beams The other parts of this intervous 50 are constituted by a light material of appropriate density, however greater than the density of the filling material of the embodiments of Figures 5 and 6 since the central portion 52 must ensure not only the connection between the two longitudinal members 51 and 42 and the filling but it must also withstand the forces exerted on this central portion 0 This embodiment however makes it possible to achieve

  a much lighter interjoin than the known interjoists.

  FIG. 8 shows a wedge for household electrical equipment. For this wedge 60, the important element consists of the reinforcements of wedges 61 connected by branches 62 simply ensuring the connection between

the corners 61.

  The wedge 70 of FIG. 9 is characterized by the edges 71 of the angled wings 72. These edges 71 are reinforced by a material of density greater than that of the wings 72. The spacer 80 of FIG. 10 is distinguished by a frame 81 with a cross section. shape of cross-and filling parallelepipeds 82 giving the whole

  a rectangular parallelepiped shape.

  The shim 9Q of FIG. 11 is distinguished by a reinforcing plate 91 and a non

  reinforced 92, the assembly forming a block.

  FIG. 12 shows a boot consisting of a boot 100 composed of an outer belt 101 and an inner lining 102 delimiting a

  cavity 103 for receiving the object to be packaged.

  The belt 101 provides the reinforcement and is high density while the portion 102 is made of a lower density material since this part ensures only the filling and holding of

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the object placed in the cavity 103.

  FIG. 13 shows a variant 110 of frames according to FIG. 12. This frame consists of a

  belt 111 convex shape and whose bottom is flat.

  FIG. 14 shows another form of box 120 whose upper edge 121 is made of a material

  different from the body 122 itself of the box.

  FIGS. 15 and 16 show reinforcement inserts, FIG. 15 showing an insert 130 with reinforced zones 131, and FIG. 16 a plate-like support 140 with an edge and including

reinforced parts 141.

  Generally speaking, although the description

  Above all, it is envisaged to locally reinforce products intended for packaging or packaging, the process according to the invention also allows the production of products formed from two materials having different characteristics such as the structure

  in volume, surface condition, color, etc. 0.

  The method of manufacturing the different parts according to FIGS. 5 to 16 is that described with reference to FIGS. 4A-4B. For all these parts, the elements such as the reinforcing elements 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141 are made during a first step of the process and then these elements are placed in the mold or part of the mold used for making the other parts 32, 42, 52 , 62, 72, 82,

92, 102, 122 parts.

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Claims (2)

R E V E N D I C A T IO N S   ) A method of manufacturing a piece of cellular plastic, such as polystyrene by injection molding, characterized in that during a first step, a blank is made of a first part of the piece by the filling a first molding cavity with a material of a first type and then during a second phase this blank is transferred into a manufacturing mold for filling-filling normally around or against the blank with the aid of a material of a second type, and then the assembly thus produced is made to follow the cycle normal manufacturing.   The method of claim 1, wherein   terized in that one realizes the first and the second   partly by the same material but of different density   annuity. 3) Part particular packaging product such as wedge, support or formwork, such as interjoists, characterized in that it consists of a single piece comprising parts of density of different matter.   ) Part according to claim 3, characterized in that it consists of a interjoists (30, 40, 50) having reinforcing elements selected from the group formed by a vault (33), a structure (41) with angles ( 42) and sleepers (43),   lateral angles (51), these reinforcing elements   being of a stronger material than the material   wherein these elements are partially embedded.    ) Part according to claim 3, characterized in that it is constituted by a wedge for equipment including household appliances comprising reinforcing elements selected from the group formed by wedges (61), longitudinal members (71), crosses ( 81), plates (91) made of a material stronger than the material 2-540037   in which these elements are at least partially embedded 6) Part according to claim 3, characterized in that it consists of a box (100, 110, 120), at least partially provided with a reinforcement surround (101, 111 , 121) made of a stronger material than the other parts of the box 7 :) Piece according to any of the   Claims 3 to 6 characterized in that the material   constituting the reinforcing elements (31-141) is the same as that constituting the other parts of the workpiece but its density is stronger.