CH659212A5 - PROCESS FOR MANUFACTURING A PART IN SYNTHETIC ALVEOLAR MATERIAL AND A PART OBTAINED. - Google Patents

Description

The present invention relates to a method of manufacturing a part made of synthetic material, in particular polystyrene according to the preamble of claim 1, 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 others 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 system, 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 out of expanded polystyrene, it is necessary to take account of a specification which wants that the slabs thus produced can resist a load of 150 daN, which requires the realization of part having a density of about 20 to 25 gr / 1. However, despite this, the support spoilers in between are 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), results in a relatively high cost of products, calling into question its competi-vity.

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, 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 for its function.

To this end, the invention relates to a method as defined in the characterizing part of claim 1.

According to an interesting aspect,

the two materials are materials of the same type but of different density.

According to another aspect, 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 sketches of parts of parts.

The inserts currently used are parts whose injection is complete, 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 brought to final dimensions . During this final phase, all the blanks are baked at the final temperature and are expanded, which ensures the interpenetration of the junction surfaces of the different stumps and consequently excellent joining of the parts (blanks) between them increasing the mechanical resistance from 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 parts obtained by implementing the method have interesting characteristics linked to the shape of the various reinforcing parts.

According to a first aspect, the part is constituted by an 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.

5

10

15

20

25

30

35

40

45

50

55

60

65

3

659,212

According to another aspect, the part is constituted by a wedge 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 aspect, the part consists of 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 aspect, the material constituting the reinforcing elements is the same as that constituting the other parts of the part, but its density is higher.

The present invention will be described by way of example and with the aid of the appended drawings in which:

- Figure 1 is a diagram of a known interjoist made of expanded polystyrene placed on two beams.

- Figures 2A and 2B respectively show a plan view, a perspective view of a wedge known for household appliances.

- Figures 3A and 3B are two sectional and plan views respectively of a slab and a block, according to the invention.

- Figures 4A and 4B show the two main stages of the product manufacturing process according to the invention.

- Figures 5 to 16 are perspective views of different products obtained by the method according to the invention, the reinforcing parts being shown in solid lines, and the outline of the parts in thin lines.

According to FIG. 1, the known interjoist 1 made of expanded polystyrene, comprises two lateral spoilers 2 by which the interjoist 1 rests on the wings of the beams 3. FIG. 1 shows the possible break line 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 whose shape, 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 whole of the wedge 5 must resist the weight of several devices stacked one on top of 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 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.

The interjoist 10 of FIG. 3A consists of a reinforcement part 11, inside, 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, is made up 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 serves of support for the object to be packaged (that is to say that the 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 with the aid of FIGS. 4A - 4B.

Figure 4A shows a first step in the process. During this first step, the blank 15 is produced corresponding to a part of the part. This is done by injecting a first type of material into the cavity 16 of the mold 17. Then this material thus injected is partially cooked (that is to say a rise in temperature sufficient to ensure the setting and its keeping in the form of the material inside the mold cavity (16), but this shaping is not pushed to the final limit.

According to FIG. 4B, during a following step (for example the second and only following step), the blank 15 produced is transferred and deposited as indicated above in the cavity 18 of the mold 19, then the material corresponds to 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 mold is filled with two different materials, and the normal manufacturing cycle is 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 carry out the final 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 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, while for the molding of the second part or of the following parts, a lower density is produced, in gradation for the successive or varying blanks. 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 shape.

It is necessary that this blank 15 or the successive blanks be strong enough to be transferred and deposited in the mold making the final part and that the blank is not 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 part, it is important that the different blanks are secured to each other at their intermediate surface (that is to say the surfaces along which the blanks are in contact l 'one with the other).

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 other transformations 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, the molding is done in 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 process can be implemented on so-called “Process” machines, that is to say which include means making it possible to create a partial vacuum inside the molds to accelerate the cooling of the parts and reduce the cycle. of work. Indeed, this process has no influence on the molding process.

5

10

15

20

25

30

35

40

45

50

55

60

65

659,212

4

Figures 5 to 13 are perspective views of different parts obtained by the method according to the invention, in which the reinforcing elements are shown with dark lines while the apparent outline of the complete parts is shown in thin lines.

Figure 5 shows a first embodiment of an inter-you 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 between-you 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 the most fragile part of the interjoist at the level of the spoilers by which it is supported. 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 70 in 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 FIG. 10 is distinguished by a framework 81 with scetion in the form of a cross 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 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 the object placed in the cavity 103. 20 The figure 13 shows a variant 110 of frames according to FIG. 12. This frame consists of a belt 111 of convex shape and the bottom of which 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 30 comprising reinforced parts 141.

The method of 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.

R

5 sheets of drawings

Claims (9)

659212 1. A method of manufacturing a part of cellular synthetic material, in particular of polystyrene, by injection molding, characterized in that during a first step, a first part of the part is produced by the filling of a first molding cavity using a material of a first type, in that during a second step, this blank is transferred to a manufacturing mold to perform overmolding using of a material of a second type, and in that the stages of cooking, expansion, cooling and ejection are carried out. 2. Method according to claim 1, characterized in that the first and second stages are carried out using the same material but of different density. 2 3. Part obtained by the method according to claim 1. 4. Part according to claim 3, characterized in that it is a wedge, a support, a formwork or a interjoist. 5. Piece according to claim 3 or 4, characterized in that it consists of a single piece comprising parts of different density. 6. Part according to one of claims 3 and 5, characterized in that it is constituted by an interjoist (30, 40, 50) comprising reinforcing elements consisting of a vault (33), a structure ( 41) with angles (42) and crosspieces (43) or lateral angles (51), these reinforcing elements being made of a more resistant material than the material in which these elements are partially embedded. 7. Part according to one of claims 3 and 5, characterized in that it is constituted by a wedge for equipment in particular household appliances comprising reinforcing elements consisting of corners (61), rails (71), cross (81 ) or plates (91) made of a more resistant material than the material in which these elements are at least partially embedded. 8. Part according to one of claims 3 and 5, 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. 9. Part according to one of claims 3 to 8, 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 greater.