CHAMBER FOR STEAM MOULDING OF EXPANDED OR CELLULAR MATERIALS OR FOAMS

Abstract

The invention relates to a chamber for steam moulding expanded or cellular materials or foams comprising an enclosure comprising at least two parts (3a, 3b), at least one part being movable to allow it to be opened and closed, and the surfaces of which are partially covered with an insulating coating, in particular the inner surface of the enclosure or the outer surface of the steam inlets.

Claims

1. A chamber for steam moulding of expanded or cellular materials or foams comprises an enclosure comprising at least two parts, at least one part being movable to allow it to be opened and closed, the enclosure comprising at least one steam inlet, and at least one cellular bead injector, wherein the surfaces of the enclosure and/or the steam inlet are at least partly covered by a thermally insulating coating.

2. The chamber according to claim 1, in which at least 50% of the outer surface of the steam inlets is covered by the insulating coating.

3. Chamber The chamber according to claim 1, in which the inner surface of the enclosure is at least 50% covered by an insulating coating.

4. The chamber according to claim 3, in which the insulating coating applied to the inner surface of the enclosure is arranged so as not to be in direct contact with the steam.

5. The chamber according to claim 3, in which the insulating coating applied to the inner surface of the enclosure is covered by a plate of thermally conductive material.

6. The chamber according to claim 5, in which the plate of thermally conductive material comprises aluminium, stainless steel and/or copper.

7. The chamber according to claim 5, in which the plate of thermally conductive material has a coefficient of thermal conductivity of between 200 and 400 W.Math.m.sup.?1K.sup.?1.

8. The chamber according to claim 5, wherein the plate of thermally conductive material has a coefficient of linear expansion from 20 to 100? C. of between 15?10?6 and 30?10?6.

9. The chamber according to claim 5, in which the thickness of the plate of thermally conductive material is between 2 and 5 mm.

10. The chamber according to claim 1, in which the insulating coating is between 1 and 5 mm thick.

11. The chamber according to claim 1, in which the insulating coating comprises mineral particles.

12. Use of a thermally insulating coating for at least partially insulating a steam moulding chamber for expanded or cellular materials or foams.

13. The use according to claim 12, in which the insulating coating is applied to the frame of the moulding enclosure, inside the steam chambers and/or to the outer surfaces of the steam passage areas or lines, the coating not being in contact with the steam.

14. The chamber according to claim 2, in which the inner surface of the enclosure is at least 50% covered by an insulating coating.

15. The chamber according to claim 4, in which the insulating coating applied to the inner surface of the enclosure is covered by a plate of thermally conductive material.

16. The chamber according to claim 6, in which the plate of thermally conductive material has a coefficient of thermal conductivity of between 200 and 400 W.Math.m?1K?1.

17. The chamber according to claim 6, wherein the plate of thermally conductive material has a coefficient of linear expansion from 20 to 100? C. of between 15?10?6 and 30?10?6.

18. The chamber according to claim 7, wherein the plate of thermally conductive material has a coefficient of linear expansion from 20 to 100? C. of between 15?10?6 and 30?10?6.

19. The chamber according to claim 6, in which the thickness of the plate of thermally conductive material is between 2 and 5 mm.

20. The chamber according to claim 2, in which the insulating coating is between 1 and 5 mm thick.

Description

[0066] The invention will be better understood with the aid of the description of several embodiments, corresponding to the drawing in which:

[0067] FIG. 1 shows a steam chamber according to the prior art (JP3874708).

[0068] FIG. 2 shows a perspective view of a first embodiment of a chamber for steam moulding expanded or cellular materials or foams in an open configuration according to the invention.

[0069] FIG. 3 shows a side view of the chamber shown in FIG. 2 in its closed configuration.

[0070] FIG. 4 is a cross-sectional exploded view of the steam chamber shown in FIG. 2 in its open configuration.

[0071] FIG. 5 is a perspective view of a steam deflector according to the invention installed in the chamber shown in FIG. 2.

[0072] FIG. 6 is a schematic cross-sectional view of an arrangement of the various layers of the enclosure shown in FIG. 2.

[0073] The features, variants and different embodiments of the invention may be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive. In particular, it is possible to imagine variants of the invention comprising only a selection of features sufficient to confer a technical advantage and/or to differentiate the invention from the prior art.

[0074] With reference to FIGS. 2 to 6, a chamber 1 for steam moulding expanded or cellular materials or foams comprises an enclosure 3 with at least two distinct parts, 3a and 3b. Part 3a is mobile while part 3b is fixed, to enable the enclosure 3 to be opened and closed. The fixed part 3b interlocks with the moving part 3a during operation to enable the moulded part to be produced.

[0075] In this non-limiting example, the enclosure 3 comprises a mould 4 with perforated cavities 5; here, four cavities 5 are shown. The mould 4 consists of a casing whose role is to hold the perforated cavities 5 used to obtain the desired part shape.

[0076] The mould 4 is in two distinct parts with one part 4a connected to part 3a of the enclosure and another part 4b connected to part 3b of the enclosure.

[0077] Part 4a of mould 4 supports a punch part of cavity 5. The other part 4b of the mould supports the die part 5b of the perforated cavity 5. When the enclosure is closed, the two parts 5a and 5b of the cavities are connected so as to delimit the volume of the part to be moulded.

[0078] The inside of the cavities 5 is designed to be in contact with expanded or cellular materials or foams. In this case, the cavities are made of aluminium. They are perforated. The perforations in the cavities are dimensioned to be smaller than the beads of the cellular material, but large enough to allow the passage of steam into the cavity, through these beads.

[0079] The mould 4 includes an ejection system 6 for the moulded part. The ejection system here comprises eight ejectors 6, which pass through the large side of the movable part 3a of the enclosure and emerge inside the cavities 5. When the ejectors 6 are activated, when the mould 4 is open, they exert pressure on the moulded part to detach it.

[0080] Enclosure 3 comprises a rigid frame and sides, on which are arranged fluid connection systems between the interior of the enclosure and the exterior of the enclosure.

[0081] In particular, there is a water inlet 7, in this case two water inlets, passing through the large side of the movable part 3a of the enclosure and intended to conduct liquid water to sprays installed in the enclosure, directed towards the cavities 5. This water is used to cool the cavities 5 to set the material after baking. The water inlet 7 helps to cool the mould cavity 4. The water inlet 7 is designed to operate discontinuously and is well known to a skilled person.

[0082] Steam inlets 8, in this case four steam inlets, are also located opposite each other on the two opposite parts of the enclosure 3a and 3b, at the top of the enclosure. They are designed to allow steam to penetrate the enclosure 3 and the mould 4 such that it passes through the cavities 5 for welding the cellular material.

[0083] Here too, as is generally the case, the steam inlets 8 can also function as air inlets, to help eject the part from the cavity when it is opened.

[0084] The cellular beads injectors 9, in this case eight injectors, pass through the large side of the movable part 3a of the enclosure and emerge inside the perforated cavities 5 of the mould 4 (not shown).

[0085] The bead injector 9 is designed to operate discontinuously and is well known to a skilled person.

[0086] Valves (not shown) are used to open and close these various injectors at the appropriate moments in the moulding cycle.

[0087] The expanded or cellular material or foam introduced into the cavities via the injectors 9 can be polystyrene, polypropylene, polyethylene and/or polystyrene/polyethylene, for example.

[0088] Enclosure 3 also includes at least one line for applying vacuum to extract the air and gas still present in the mould after the water-cooling phase. Preferably, the vacuum application line is connected to a vacuum pump located close to chamber 1. This equipment is well known to a skilled person.

[0089] The enclosure 3 comprises locking means 11 designed to keep the enclosure 3 sealed during successive injections of beads into the cavities 5, and of steam and water towards the cavities 5. These locking means 11 can be two-part fasteners placed opposite each other around the perimeter of the enclosure parts 3a and 3b. They interlock with each other when chamber 1 is closed. Here, twelve fasteners (three per side of the enclosure) are fixed to the side parts 3a and 3b of the enclosure. The number and/or type of fasteners may depend on the dimensions of the chamber.

[0090] The enclosure 3 comprises reinforcements such as, for example, stiffeners 12 placed along the lateral side of part 3a of the enclosure. The ends of the stiffeners are fixed by screws 13 to the rear frame 14 of part 2a of the additional chamber. These screws 13 can be, for example, of type FH M12?60 mm.

[0091] Part 3b of the enclosure includes a sprinkler circuit 15 at the rear to regulate the temperature of the mould 4.

[0092] Steam deflectors 16 are installed in the enclosure 3 opposite the steam inlet to ensure faster dispersion of steam in the enclosure (FIG. 5). The deflector 16 is fixed, for example, to the plate a few centimetres from the steam inlet 8 using screws 16a.

[0093] An insulation layer 17, here for example a rigid layer of epoxy resin, is placed on the inside faces of the enclosure 3 (FIG. 4), in particular on the side faces (on which the enclosure opens) as well as on the large faces. Conductive metal plates 19 cover the insulation.

[0094] The insulating layer 17 comprises two layers 17 and 17a. It is assembled inside the enclosure 3 using a mortise and tenon system at the corners (FIG. 6) to prevent the steam from coming into contact with the edges and/or corners of the frame, thereby preventing the formation of condensation.

[0095] The insulation layer 17, 17a is positioned and fixed to the four sides of the frame of the enclosure 3, for example using screws 18.

[0096] The two-layer composition of the insulation makes it possible to increase and/or combine the thermal properties of the insulation. In FIG. 5, an additional insulation layer 17a covers the insulation layer 17.

[0097] Insulation 17, 17a can have a total thickness of between 15 and 45 mm. It is possible to have different thicknesses between 17 and 17a. It is also possible to combine more than two layers.

[0098] Insulators 17 and 17a are chosen according to technical criteria such as good thermal and mechanical resistance, a low expansion coefficient and good stability with respect to heat and humidity over the period of use. For example, an insulator could be an epoxy resin.

[0099] Examples of optimal ranges for the mechanical properties of insulation are described in Table 1 below:

TABLE-US-00001 TABLE 1 Test Value Technical criteria method range Density (in g/cm.sup.3) ISO 1183 1.70-2 Thermal conductivity ISO 8302 0.20-0.40 (in W/mK) Thermal resistance (in IEC 216 150-250 ? C.) Compressive strength ISO 604 400-550 (in MPa) Flexural strength (in ISO 178 350-450 MPa) Dielectric strength IEC 243-1 10-20 (in kV/mm)

[0100] A non-limiting example of insulation suitable for this invention is the one sold under the trade name Deltherm 68.890 by BASFF Thermal Engineering SRL or EPGM 203 sold by Melpro SAS.

[0101] The plate of thermally conductive material 19 covering it is in this case made of aluminium, a material chosen for its properties as well as its affordability. However, other materials can also be used, such as stainless steel, copper, alloys or composites.

[0102] The characteristics of copper, stainless steel and aluminium are detailed in table 2 below:

TABLE-US-00002 TABLE 2 Stainless Aluminium steel Copper Thermal 237 15-20 390 conductivity (W-m.sup.?1-K.sup.?1) Coefficient of 15 ? 10.sup.?6 16.5 ? 10.sup.?6 30 ? 10.sup.?6 linear expansion from 20? to 100? C. Density (in g/cm.sup.3) 2.7 7.8-7.9 8.96 Melting point (in 660.3 1085 ? C.) Poisson's ratio 0.24 to 0.33 0.33 Young's modulus 69 200 124 (in GPa) Specific heat (in 897 500 385 J .Math. k.sup.?1 .Math. kg.sup.?1)

[0103] The thermally conductive material 19 preferably has a thermal conductivity of between 230 and 450 W-m.sup.?1-K.sup.?1. The thermal conductivity of a material is a physical quantity that characterises its ability to diffuse heat in media without any macroscopic displacement of matter. Aluminium and copper therefore have good conductivity.

[0104] The plate of thermally conductive material 19 preferably has a low coefficient of linear expansion, i.e. a coefficient of linear expansion from 20 to 100? C. between 15?10.sup.?6 and 30?10.sup.?6.

[0105] The plate of thermally conductive material 19 covers almost the entire surface of the insulator, which itself covers almost the entire inside wall of the enclosure. Although less cover would probably be less effective, it would still be more profitable than not having any. The conductive material therefore preferably covers at least 70% of the insulating layer 17 or 17a, more preferably 80%, even more preferably 90%, and most preferably the entire insulating layer 17 or 17a.

[0106] Preferably, the thickness of the plate of thermally conductive material 19 is 5 mm here. This helps to provide sufficient rigidity for its integration into the enclosure 3 and gives it good durability, without unduly weighing down the device and the metal mass to be heated.

[0107] The plates 19 are fixed to the insulation 17, 17a using screws 20, in this case made of stainless steel to withstand the damp conditions expected inside the enclosure, and do not interfere in any way with the properties of the plate 19.

[0108] A non-limiting example of a plate of thermally conductive material 19 suitable for this invention is the one sold under the trade name AG 3C 5083 by Eyrolliage?.

[0109] The characteristics of the AG 3C 5083 plate are described in Table 3 below:

TABLE-US-00003 TABLE 3 AG 3C 5083 plate Modulus of elasticity (MPa) 71000 Modulus of rigidity (MPa) 26800 Poisson's ratio (v) 0.33 Solidity temperature (in ? C.) 580 Melting point (? C.) 640 Specific heat (in J kg ? 1 K ? 1) 899 Coefficient of thermal 23.8 expansion (in ?m m ? 1 K ? 1) Density (in kg m ? 3) 2660 Resistivity (in n?m) 60 Thermal conductivity (in ?) 117 Electrical conductivity (in 28.5 % IACS)

[0110] FIGS. 2 to 6 illustrate a specific embodiment of the chamber of the invention. A person skilled in the art will be familiar with the operating principle of such chambers and the technical variations that can be made to them, depending on the type of cellular material used, the size and shape of the parts to be moulded, etc.

[0111] The innovation here lies in the insulating layer 17 combined with a plate of thermally conductive material 19.

[0112] During a parts moulding process, the enclosure is initially closed, cellular foam beads are injected into the cavities 5, steam is then injected into the enclosure 3 and the mould 4 so as to penetrate the cavities 5 to weld the cellular beads. Liquid water is then sprayed onto the cavities to set the moulded parts. A vacuum stage extracts residual moisture and accelerates stabilisation of the moulded part. The enclosure 3 is then opened, the part ejectors 6 activated and/or a stream of air is applied to eject the parts. The enclosure 3 is then closed again for a new cycle.

[0113] Thanks to the combination of insulation and plates of conductive material 19, energy loss from the process is considerably reduced. Only the plates of conductive material 19 are subject to temperature variations during each cycle, which represents a much smaller volume of material than the frame and walls of the enclosure. In addition, the temperature of the plates of conductive material 19 does not drop considerably during the cooling phase of the part, thus preventing the moisture introduced into the chamber (steam, water spray) from condensing on these walls and in the chamber in general, thereby avoiding manufacturing defects due to condensation.

[0114] The invention has also been implemented in another way, by replacing the insulating plates 17 and 17a with an insulating coating.

[0115] The thermal insulation coating is in this case a white hydrophobic paint comprising a mixture of styrene and acrylic polymers (formaldehyde, methyl acrylate and styrene) in an aqueous base, fire inhibitors and retardants and closed-cell microgranular ceramic additives with a thermal conductivity of around 1 mW/m. ? C. per layer. It was applied by brush in several coats (typically 5 coats of 0.5 mm) until a coat of 2-3 mm was obtained on the inner surface of the enclosure (instead of insulation 17 and 17a) and covered with a conductive aluminium plate (2.5 mm thick). A watertight seal, in this case an acetic silicone seal for high-temperature applications, is applied around the perimeter to prevent any contact between the process steam and the paint.

[0116] Paint was also applied by brush at a thickness of 1.5 to 5 mm to the external, visible parts of the machine, in which steam circulates.

[0117] A standard production cycle was carried out. It was found that the temperature recorded on the outside of the enclosure was 50% lower than the temperature recorded for the same production run without paint (43.8? C. compared to 84.2? C. without insulation). Steam consumption is reduced by 39% compared to a cycle without insulation.

[0118] It is anticipated that by insulating the entire chamber, steam savings could reach 50%.

[0119] The paint could also have been applied using a spray gun.

[0120] To improve the adhesion of the paint to the various surfaces, the first coat can be diluted with water, for example to 50% by volume.

[0121] In a first aspect of the invention, a chamber for steam expansion moulding (1) of expanded or cellular materials or foams comprises an enclosure (3) comprising at least two parts (3a, 3b), at least one part being movable (3a) to allow it to be opened and closed, and the inner surface of which is at least partly covered with insulation (17), characterised in that a plate of thermally conductive material (19) covers the insulation (17).

[0122] In the chamber of the first aspect, the enclosure (3) may comprise a mould (4) with at least one perforated cavity (5). In the chamber of the first aspect, the enclosure (3) may comprise fluid connection systems between the inside and outside of the enclosure (3), the fluid connections being at least one water inlet (7), at least one steam inlet (8), and at least one cellular bead injector (9).

[0123] In the chamber of the first aspect, the inner surface of the enclosure (3) may be covered across at least 50% by the insulation (17), preferably at least 70%, more preferably at least 90%.

[0124] In the chamber of the first aspect, the insulation (17) can be assembled inside the enclosure (3) using a mortise and tenon system at the corners.

[0125] In the chamber of the first aspect, the insulation (17) may comprise one or more superimposed insulation layers (17a), possibly of different types.

[0126] In the chamber of the first aspect, the plate of thermally conductive material (19) comprises aluminium and/or copper.

[0127] In the chamber of the first aspect, the plate of thermally conductive material (19) can have a thermal conductivity coefficient of between 200 and 400 W.Math.m.sup.?1K.sup.?1.

[0128] In the chamber of the first aspect, the plate of thermally conductive material (19) may have a coefficient of linear expansion from 20 to 100? C. of between 15?10.sup.?6 and 30?10.sup.?6.

[0129] In the chamber of the first aspect, the plate of thermally conductive material (19) preferably covers at least 70% of the insulation (17).

[0130] In the chamber of the first aspect, the thickness of the plate of thermally conductive material (19) is between 2 and 7 mm. The various features proposed for the chamber of the first aspect may be combined and are not mutually exclusive.

[0131] In a second aspect of the invention, a chamber for steam moulding (1) of expanded or cellular materials or foams comprises an enclosure (3) comprising at least two parts (3a, 3b), at least one part being movable (3a) to allow it to be opened and closed, the enclosure (3) comprising at least one steam inlet (8), and at least one cellular bead injector (9), characterised in that the surfaces of the enclosure and/or the steam inlet are at least partly covered by a thermally insulating coating.

[0132] In the chamber of the second aspect, at least 50% of the outer surface of the steam inlets can be covered by the insulating coating, preferably at least 70%, more preferably at least 90%. In the chamber of the second aspect, at least 50% of the outer surface of the enclosure (3) can be covered by the insulating coating, preferably at least 70%, more preferably at least 90%. In the chamber of the second aspect, the insulating coating applied to the inner surface of the enclosure is arranged so as not to be in direct contact with the steam.

[0133] In the chamber of the second aspect, the insulating coating applied to the inner surface of the enclosure may be covered by a plate of thermally conductive material.

[0134] In the chamber of the second aspect, the plate of thermally conductive material (19) may comprise aluminium, stainless steel and/or copper.

[0135] In the chamber of the second aspect, the plate of thermally conductive material (19) can have a thermal conductivity coefficient of between 200 and 400 W.Math.m.sup.?1K.sup.?1.

[0136] In the chamber of the second aspect, the plate of thermally conductive material (19) may have a coefficient of linear expansion from 20 to 100? C. of between 15?10.sup.?6 and 30?10.sup.?6. In the chamber of the second aspect, the thickness of the plate of thermally conductive material (19) may be between 2 and 7 mm. In the chamber of the second aspect, the insulating coating may be between 1 and 5 mm thick, preferably between 2 and 4 mm. In the chamber of the second aspect, the insulating coating may comprise mineral particles.

[0137] The various features proposed for the chamber of the second aspect may be combined and are not mutually exclusive.