WO1984002876A1

WO1984002876A1 - Method for manufacturing an alveolar synthetic material part and parts obtained thereby

Info

Publication number: WO1984002876A1
Application number: PCT/FR1984/000021
Authority: WO
Inventors: Guy Lalloz; Gabriel Joly
Original assignee: Saplest
Priority date: 1983-01-31
Filing date: 1984-01-30
Publication date: 1984-08-02
Also published as: BE898810A; JPS60500708A; FR2540037A1; GB2146945A; FR2540037B1; GB8423871D0; DE3490031T1; GB2146945B; CH659212A5

Abstract

a) Method for manufacturing an alveolar synthetic material part, such as polystyrene by injecting molding. b) Method characterised in that during a first step a preform (15) is made in a first mould with a material of a first type and, during a second step, said preform (15) is transferred into a manufacturing mould (19) that is filled (18) with a second material. Alternatively, both materials are the same, but with different densities. c) The invention relates to the manufacturing of alveolar parts particularly intended to the building industry, to the packaging of mechanical parts for the motor vehicle industry and to various industrial fields.

Description

"Method of manufacturing a part in cellular synthetic material and parts obtained".

The present invention relates to a method for manufacturing a part made of cellular or expanded synthetic material such as polystyrene by injection molding, as well as the parts obtained. The multiple advantages of expanded synthetic materials such as polystyrene, have led to a significant development in the use of this material for the manufacture of the most different parts using the characteristics of insulation, rigidity and lightness of this material.

Thus an important field of use of such expanded materials is the building for the manufacture of interjoists among other things in expanded polystyrene or the manufacture of wedging elements used for the packaging of fragile products. , such as household electronic equipment (television, radio receiver, HIFI, etc.).

Depending on the resistance that the part must have, the density of the polystyrene is modified during injection molding.

Thus, for the realization of interjoists in expanded polystyrene, it is necessary to take into account a specification which wants that the slabs thus produced can resist a load of 150 daN, which requires the production of parts having a density of about 20 to 25 gr / 1. However, despite this, the support spoilers

O PI 2 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 entire product is chosen so that these spoilers resist the expected loads. However, the increase in the cost of raw materials and fuel (necessary for injection molding), result in a relatively high cost of products, calling into question its competitiveness. Similar problems arise for parts used substantially under similar conditions such as, for example, wedging parts used for electronic devices. These wedging pieces are in the form of rings or flanges of rectangular section, which surround the parallelepipedal casing of the electronic device, to ensure its positioning in the cardboard box and allow the boxes to be stacked.

In general, the parts of the type of those above have a certain shape, but only certain parts of the part must have an appropriate resistance, the other parts constituting only the necessary filling of the volume.

^' This therefore results in a loss of material and manufacturing cost. The object of the present invention is to create a process for manufacturing parts of expanded synthetic material, in particular polystyrene, by injection molding, making it possible to achieve a significant saving in material and weight without reducing the resistance characteristics of the product produced, by adapting the product structure to its function.

To this end, the invention relates to a method characterized in that, during a first step, a first part of the part is made by filling a first molding cavity using 'a material of a first ^" type then during a

WIPO 3 second phase, this blank is transferred to a manufacturing mold for filling normally around or against the blank using a material of a second type and then the assembly thus made follows, the cycle normal manufacturing.

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 manufacturing cycle using a hot mold and a cold mold (Ritter process), the blank is placed in the hot mold.

The method according to the invention offers considerable advantages both in the manufacture and in the distribution and use of the parts thus produced.

Indeed, the process is totally different from the manufacturing process of molding a part with inserts because the inserts are produced according to a separate process and do not constitute blanks for parts of parts.

The inserts currently used are parts whose injection is finished, that is to say whose heat treatment is finished and these parts are of final dimensions. Contrary to this, the method according to the invention consists in making successive drafts of parts of the part then, when all the drafts are made, in carrying out the final heat treatment (baking), treatment during which the part is put in the final dimensions. During this final phase, all the blanks are baked at the final temperature and are expanded, which ensures the inter¬ penetration of the joining surfaces of the different blanks and consequently excellent joining of the parts (blanks) between them increasing the resistance mechanics of the whole. Such a connection by nesting of the contact surfaces, by local deformation of these surfaces, interpenetration by the balls of expanded material, etc., is not possible in the case of inserts since these are necessarily finished parts. . Moreover, this is even necessary because the blanks would not have the resistance necessary for handling, storage and transport.

The invention also relates to the products obtained by implementing the method.

These products or parts molded in several stages have interesting characteristics linked to the shape of the various reinforcing parts. According to a first characteristic, the part is constituted by a interjoist comprising reinforcing elements chosen from the group formed by a vault, a structure with angles and crosspieces, lateral angles, these reinforcing elements being made of a more resistant material than the material in which these elements are partially embedded.

According to another characteristic, the part is constituted by a shim for equipment, in particular household appliances, comprising reinforcing elements chosen from the group formed by corners, longitudinal members, crosses, plates made of a material more resistant than the material in which these elements are at least partially embedded.

According to another characteristic, the part is constituted by a box, fish crate, fruit crate, provided at least partially with a reinforcing frame made of a more resistant 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 part but its density is higher.

WIPO The present invention will be described in more detail with the aid of the appended drawings in which:

- Figure 1 is a diagram of an interjoist made of expanded polystyrene placed on two beams, - Figures 2A and 2B respectively show a sectional view, a perspective view of a wedge for household appliances.

- Figures 3A and 3B are two sectional views of a slab and a block, according to the invention, - Figures 4A and 4B ^' represent the two main stages of the product manufacturing process, according to the invention,

- Figures 5 to 18 are perspective views of different products according to the invention, the reinforcing parts being shown in solid lines and in gray, and the outline of the parts in thin lines.

According to Figure 1, 1 * known interjoist 1 made of expanded polystyrene, has two lateral spoilers 2 by which 1 * interjoist 1 rests on the wings of the beams 3. Figure 1 shows the possible line of rupture 4 at each of the spoilers 2.

To avoid this rupture, it is necessary to make the slab 1 in expanded polystyrene, with a relatively high density of the order of 25 to 30 gr / 1 to satisfy the load conditions which this interjoist must theoretically resist.

FIGS. 2A and 2B show a wedge 5 in the form of a rectangular ring provided with an opening 6 the shape of which, for example rectangular, is adapted to that of the housing of the device to be packaged. The wedge 5 is placed on the housing as shown in Figure 2B. Under these conditions, only the part to the right of the device, that is to say the opening 6 in each of the four directions, must resist the weight of the device and the assembly of the hold 5 must withstand the weight of many 6 devices stacked on top of each 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 constraints which are exerted at the level of window 6 could not be transmitted by low density polystyrene. It is therefore necessary to increase the overall density of the product, that is to say to pass from a density of 15 gr / 1 to for example a density of 30 gr / 1.

FIGS. 3A and 3B schematically show a interjoist and a wedging piece manufactured according to the invention. L * entrevous 10 of Figure 3A consists of a reinforcing part 11, interior ,, surrounded by a part 12 giving the appropriate overall shape but having only a very reduced support function.

The packing wedge 12 ′, according to FIG. 3B, consists of a reinforced part 13 and an external part 14. This assumes that the orientation of the part is not arbitrary and that the reinforced part 13 always serve as a support for the object to be packaged (that is to say that part 13 is located below the corresponding part of the part).

The method of manufacturing parts such as those given by way of examples in FIGS. 3A and 3B will be described below using FIGS. 4A - 4B.

Figure 4A shows a first step in the process. During this first step, the blank 15 corresponding to a part of the part is filled. This filling is done by injection of a prerr.ier type of material into the cavity 16 of the mold 17. Then this material thus injected is partially cooked (that is to say sufficient temperature rise to ensure the setting and its holding in the form of the material to

WIPO 7 inside the mold cavity 16). This shaping is however not pushed to the final limit.

According to FIG. 4B, during a next step (for example the second and only next step), the blank 15 produced is transferred and deposited as indicated above in the cavity 18 of the mold 19, then the material corresponds by example to a second type to form the second part of the part, and is injected into 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 part is filled with as many different materials as there are blanks, plus one, which is the final filling material of the cavity 18. According to the method described above, the material used to achieve the definitive filling of the second part of the part in the cavity 18, can be the same material or a different material from that used for the blank 15. In general, as the blank 15 is intended to form the reinforcement of the part, its resistance must be greater than that of the other parts of the part also its density must it be greater than that of the other parts of the part. For this, during the production of the blank, a blank of high density is formed, suitable, whereas .for the filling of the second part or of the following parts, a lower density is produced, in gradation for the blanks succes¬ sives or varying according to a specific order. It is essential that the molding operations carried out in the phases preceding the final phase be

WIPO 8 at least partially of the pre-molding operations, that is to say giving a blank and not one. product having its final form.

This blank 15 or the successive blanks must be solid enough to be transferred and deposited in the mold making the final part and the blank must not be destroyed during the final filling operation of the part. .

To improve the solidity of the manufactured product as well as the mechanical resistance not only of the different parts of the part, but also of the whole of the part, it is important that the different blanks are secured to each other at level of their intermediate surface (that is to say the surfaces along which the blanks are in contact with one another).

This connection between the different parts of the part is carried out during the part molding operation which consists in cooking at the final temperature of the steam (in the case of an expanded material, such as polystyrene) .

Different installations, not shown, can be used for implementing the method according to the invention and these installations require no further trans¬ formations than the modification of the molds. The method according to the invention can be used on traditional machines. In the case of a part in two parts, according to the invention, the traditional molding consists of two molds, one for the first draft, 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 during these recent years. In this case, the final filling is done in the hot mold.

Finally, the method can be implemented on machines called "Process", that is to say which include 9 means making it possible to create a partial vacuum inside the molds to accelerate the cooling of the parts and reduce the working cycle. Indeed, this process has no influence on the molding process.

FIGS. 5 to 13 are perspective views of different parts, according to the invention, in which the reinforcing elements are shown with dark lines and the faces of these elements are in gray while the apparent outline of the complete parts is shown in fine lines.

FIG. 5 shows a first embodiment of an interjoist according to the invention. This interjoist 30 includes a reinforcement vault 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 on one side (on the right according to FIG. 5) by a plate 35 intended to cover the beam from below (not represented) who receives the interjoist. This extension 35 is necessary to ensure both the insulation and the continuity of the ceiling.

Figure 6 shows a second embodiment of a interjoist 40, according to the invention. This second mode differs 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 the weaken. Within the outline of this interjoist 40, the volumes and cavities other than those occupied by the reinforcing element 41 are occupied by a material of lower density simply ensuring the shape of the assembly and the filling.

FIG. 7 shows a third embodiment of a interjoist 50 according to the invention. This interjoist, the external shape of which is similar to that of the two previous embodiments, comprises two reinforcement beams 51 along the lateral edges, to reinforce 10 the most fragile part of the interjoist at the spoilers by which it rests on the beams. The other parts of this interjoist 50 are made of a light material of appropriate density, however greater than the density of the filling material of the embodiments of FIGS. 5 and 6 since the central part 52 must not only ensure the connection between the two longitudinal members 51 and 42 and the filling, but it must also withstand the forces exerted on this central part. This embodiment however makes it possible to arrive at a much lighter interjoist than the known interjoists.

Figure 8 shows a wedge for household appliances. For this wedge 60, the important element consists of the corner reinforcements 61 connected by branches 62 simply ensuring the connection between the corners 61.

The wedge 7θ of FIG. 9 is characterized by the edges 71 of the square wings 72. These edges 71 are reinforced by a material of density greater than that of the wings 72 _*

The wedge 80 of Figure 10 is distinguished by a frame 81 with cross-shaped section and filling parallelepipeds 82 giving the assembly a rectangular parallelepiped shape. The wedge 90 of Figure 11 is distinguished by a reinforcing plate 91 and an unreinforced part 92, the assembly forming a block.

FIG. 12 shows a box composed of a box 100 composed of an outer belt 101 and an inner lining 102 delimiting a cavity 103 intended to receive the object to be packaged. The belt 101 provides reinforcement and is of high density while the part 102 is made of a material of lower density since this part ensures only the filling and the holding of

OM

\ VI? 11 the object placed in the cavity 103.

- The: Figure 13 shows a HO variant of frames according to Figure 12. This frame consists of a belt 111 of domed shape and the bottom is flat. FIG. 14 shows another form of box 120, the upper edge 121 of which is made of a material different from the body 122 proper of the box.

FIGS. 15 and 16 represent reinforcement inserts, FIG. 15 showing an insert 130 provided with reinforced zones 131 and FIG. 16, a support 140 in the form of a plate provided with an edge and comprising reinforced parts 141.

In general, although the above description particularly considering the local reinforcement products for packaging or ^'packaging, the method according to the invention also allows the production of products made of two materials having different characteristics such as the structure in the volume, the surface condition, the color, etc. The process for manufacturing the various parts according to FIGS. 5 to 16 is that described with the aid of 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 produced during a first step of the process then these elements are placed in the mold or part of the mold used to make the other parts 32, 42, 52, 62, 72, 82, 92, 102, 122 of the parts.

Claims

12

2) The method as claimed in claim 1, characterized in that the first and second parts are produced using the same material but with a different density.

3) Part in particular packaging product such as wedge, support or formwork, such as a interjoist, characterized in that it consists of a single part comprising parts of different material density.

4 ^e ) part according to claim 3, characterized in that it is constituted by an interjoist (30, 40, 50) comprising reinforcing elements chosen from the group formed by a vault (33), a structure (41) to angles (42) and crosspieces (43), lateral angles (51), these reinforcing elements being made of a more resistant material than the material in which these elements are partially embedded.

5 °) Piece according to claim 3, characterized in that it is constituted by a wedge for equipment in particular household appliances comprising reinforcing elements selected from the group formed by corners (61), side members (71), cross (81), plates (91) * made of a material more resistant than the material f WIPO 13 in which these elements are at least partially embedded.

6 ^e ) part according to claim 3, characterized in that it is constituted by a box (100, 110, 120), provided at least partially with a reinforcing surround (101, 111, 121) in a more resistant material than the other parts of the box. ^"

7 °) Part according to any one of 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 part but its density is higher.

O PI