HK1078513A - Method and device for forming a plastic coat on a surface - Google Patents

Description

Method and device for forming a layer of plastic material on a surface

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Technical Field

The invention relates to a method and a device for forming a coating on a surface starting from a liquid or viscous composition.

The method and apparatus are particularly useful for making articles of plastics material or for applying a coating within or outside a package, but such application is not exclusive.

The invention also relates to an article obtained by the above method.

Background

The realization of the coating of the wall of the article or the wall of plastic material is now obtained by one of the following methods:

injection moulding consists in injecting a material in the liquid state into the cavity of a closed mould. The plastic material solidifies and retains the geometry defined by the mold cavity when it cools.

Compression moulding methods which consist in supplying a plastic material in liquid form into an open mould. When the mould is closed, the plastic material flows and fills the cavity of the mould. The plastic material solidifies and retains the geometry formed by the mold cavity as it cools.

Hollow body extrusion method, which consists in extruding a roll of molten plastic material, and then expanding the roll in a mould to adapt it to the geometry. The molten material in contact with the mold cools and solidifies.

Planar extrusion of films, blades or plates, which consists in continuously providing a film of plastic material in the molten state with a greater or lesser thickness and in cooling this film on a cooling roller.

Coating method consisting in continuously extruding a film of plastic material deposited on a running substrate.

Extrusion in the form of a sheath, which consists in continuously providing a tubular film of molten plastic material, then in expanding and stretching the film in air.

Pipe or profile extrusion processes which consist in continuously supplying molten plastic material, passing it in a caliper, and then cooling it in order to solidify it.

Method for coating pipes or cables, which consists in covering the travelling object with a layer of plastic material and in solidifying this layer by cooling the plastic material in water.

Thermoforming consists in heating a sheet of plastic material to a temperature below the melting temperature and then deforming the sheet of plastic material in a mould by pressure or negative pressure.

Two-way blowing method, which consists in producing a hollow body starting from an injection preform. The preform is heated to a temperature below the melting temperature of the plastic material and the plastic material is then stretched and blown in a mold. The plastic material is contacted with the mold and cooled.

The object of the invention is a method and a device for implementing said method, which allows to obtain a coating of plastic material or a wall of plastic material of an article.

Disclosure of Invention

The invention relates to a method for producing a coating on a surface, starting from a plastic material in liquid or viscous form, said plastic material solidifying once the coating has been formed, characterized in that the plastic material in liquid or viscous form is introduced into a reservoir of variable volume, at least a part of the inner wall of the reservoir being formed by a portion of the surface; the reservoir and the surface are moved relative to each other while reducing the volume of the reservoir in order to compress the plastic material and to cause the plastic material to flow through a channel connecting two surface portions disposed respectively inside and outside the reservoir, the flow rate of the plastic material through the channel being selected so as to form a coating on one of the surface portions, the thickness of the coating being smaller than the height of the channel.

The invention also relates to a device for producing a coating on a surface according to the above method, characterized in that it comprises:

-a surface to be coated;

-a reservoir of variable volume, at least a portion of the inner wall of said reservoir being formed by a portion of said surface;

-a channel connecting two surface portions arranged respectively inside and outside said reservoir, the height of said channel constituting an upper limit for the thickness of the coating to be deposited;

-means for effecting movement of said reservoir relative to said surface;

-means for reducing the volume of said reservoir when it is moved relative to each other.

The invention also relates to an article obtained by the above method, characterized in that it comprises a coating of plastic material, initially in liquid or viscous form, which, once deposited, solidifies, the inner and outer surfaces of said layer having different roughness.

Scope of application of the invention

The invention can be used in a very wide range of applications. One common feature of these applications is that the plastic material is initially in a liquid or paste state for forming the layer. The plastic material can be distinguished by the fact that it solidifies or remains liquid or paste after the layer (grease, oil) has been formed. Most applications involve plastic materials that cure after deposition. Mention may be made, among this category, of plastic materials which solidify after deposition by cooling (thermoplastic polymers), those which solidify after curing (thermosetting polymers, varnishes), those which solidify by evaporation (water-based or solvent-based paints), those which solidify by chemical reaction (glues).

Coating material

The method of forming a coating according to the invention makes it possible to obtain articles or deposits of plastic material having very different characteristics. By way of non-limiting example, the following polymers may be used:

polyolefin: PP, EPDM, PE, E/VA, E/VOH, E/EA, E/MA, PB, ion exchange polymers

Ethylene polymer: PVC, PE-HD-C, E/VA/VC, VC/VDC/AN, VC/MAH

Styrene polymer (A): PS, S/MS, S/AN, S/B, ABS, ASA

Fluorinated polymer: PTFE, FEP, E/TFE, PCTFE, PVF, PVDF

Polyamide: PA6, PA66, PA46, PA12, PA11, PA612

Polyester: PC, PET, PBT, PEN, LCP

Polymethyl methacrylate (PMMA)

Polyaldehyde (POM)

Polyurethane

Polylactic acid (PLA)

Polyacrylonitrile

polyarylethers et polyaryletherketones

Polyimide, polyimide resin composition and polyimide resin composition

Phenol/formaldehyde resins

Urea-formaldehyde resin (Polyamide plastic material)

Melamine/formaldehyde resin

Unsaturated polyester resin

Silicone resin

Epoxy resin

Net-like polyurethane

Mixtures of polymers

Feeding of the apparatus

The plastic material may be provided to the coating device in a liquid, paste or solid state. In the special case of solid feed materials, the plastic material will be melted by the coating apparatus before coating and made into a liquid or paste.

The feeding of the apparatus can be carried out according to known cavity filling techniques, i.e.

Gravity feed (solid or liquid)

-pump feeding

Feeding by worms

Injection feeding (liquid)

Feeding by manual or automatic conveying

Feeding through an extruder or an injection press

This table is not complete.

Mode of operation

The mode of operation should be based on the polymer used to form the deposit. The deposition of a thermoplastic material requires preheating the polymer in order to make the plastic material a fluid or paste in the coating apparatus and then cooling the polymer as the deposition is formed. The coating apparatus according to the invention can be heated and cooled according to the thickness of the deposit, the geometry of the part and the operating conditions.

The deposition of a thermoset polymer should include post-deposition curing of the polymer so that reticulation can be achieved. Hot or cold deposition can be carried out depending on the product to be deposited, the geometry of the part and the operating conditions (deposition rate).

Paint deposition according to the present invention includes a post-deposition volatilization phase. A furnace, hood, or other material for capturing volatiles or accelerating the volatilization process can be incorporated with the coating apparatus consistent with the present invention.

Implementation of articles or coatings of plastic material

The realization of the deposition of articles or coatings of thermoplastic material according to the invention requires the heating of the polymer to a temperature above its melting temperature in order to cause the material to flow in the coating device. The delivery temperature is increased by at least 10-20 ℃ compared with the melting temperature. For polymers with very narrow melting peaks, the delivery temperature can be fairly close to the melting temperature. As the coating is deposited on the wall, it solidifies on cooling. The coating apparatus may be heated or cooled.

Realization of articles of plastic material

The realization of a plastic material part with the apparatus according to the invention can in some cases be defined by the coexistence of at least two phases, one belonging to the coating phase of the extrusion process and the other to the compression phase of the injection or compression molding process. In this embodiment, the present invention combines the advantages of the extrusion process and the modeling process. The method according to the invention can have a low load loss and a substantially constant load loss during the coating phase, and can ensure great accuracy and maintain the appearance characteristics during the compression phase.

The invention makes it possible to obtain articles of plastic material having a thickness varying between 50 microns and 10 mm, and preferably between 0.25 mm and 2.5 mm. It is noted that thicknesses of less than 50 microns are also contemplated. The degree of fluidity is selected to be greater or lesser depending on the thickness of the part. For a particularly small wall thickness, it is preferable to use a high-fluidity polymer, while for a large wall thickness, a viscous product is preferably chosen.

The invention makes it possible to realize thin-walled (less than 0.5 mm) articles of plastic material with side walls of a length greater than 400 mm and with very little material stress in the apparatus. The invention allows a high degree of accuracy to be achieved for parts that are realized by compression.

The invention also makes it possible to realize thick-walled (greater than 5 mm) articles of plastic material with side walls of greater than 1 metre in length, and with less material stress in the plant. The invention allows a high degree of accuracy to be achieved for parts that are realized by compression.

The method according to the invention makes it possible to implement new articles which are difficult or impossible to implement with the known methods. For example, the method can produce a cylindrical box with a depth of 60 cm, a diameter of 10 cm and a wall thickness of 0.5 mm, or even a soft pocket with a thickness of 0.3 mm and a bottom with a thickness of 1 mm.

Articles realized according to the present invention generally have different properties at the inner and outer surfaces of the article part realized by the coating.

The internal coating device allows to obtain articles with high quality of the external surface (optical characteristics, external tube, roughness, etc.) which is in contact with the internal wall of the device. The inner surface of the article is cooled by convection with a gas (air, nitrogen).

The outer coating apparatus can result in an article having high quality inner surfaces (optical properties, outer tube, roughness, etc.) that contact the outer walls of the apparatus. The outer surface of the article is cooled by convection with a gas (air, nitrogen).

Implementation of the deposition of the plastic material

The coating method according to the invention can be used to coat the surface of metal, glass, plastic material, cardboard or paper with a layer of thermoplastic polymer.

For example, the present invention may apply a thermoplastic coating to the inner or outer surface of a pipe or profile. The thickness of the coating may vary between 0.05 mm and 10 mm, preferably between 0.2 mm and 2 mm.

The invention can cover the surface of an object (film, sheet, tube, section bar, object) partially or completely.

The coated article may be heated prior to or during deposition of the coating.

The surface to be coated may be pretreated prior to deposition. Examples of the pretreatment include:

chemical treatment

-Heat treatment

Physical treatment

Mechanical treatment

Drawings

The invention and embodiments according to the invention are described in detail below with the aid of the figures.

Brief Description of Drawings

Fig. 1 shows a cross-sectional view of the device and coated parts realized in a plane parallel to the direction of relative movement of the device.

Fig. 2 shows an enlarged view of the apparatus of fig. 1 at the passage.

Fig. 3 shows the device of fig. 1 in motion.

Fig. 4 is a cross-sectional view of another variant of the apparatus according to the invention.

Figures 5-9 show different operating stages of another variant of the plant.

Fig. 10-15 show different operating stages of another variant of the plant.

Fig. 16 and 17 show an apparatus for manufacturing a multilayer article.

Figure 18 shows an article obtained by the apparatus of figures 16 and 17.

Fig. 19 and 20 show an apparatus for manufacturing blown articles.

FIGS. 21-28 illustrate an apparatus for internally coating a tubular body.

FIG. 29 shows an apparatus for coating a tubular body with an outer coating.

Fig. 30 shows an apparatus identical to that of fig. 29, but additionally comprising means for forming a shoulder and a tip.

Figure 31 shows an apparatus for manufacturing a tube.

Figure 32 shows a device that can produce a protrusion.

Figure 33 shows an apparatus which can produce a double claw protrusion.

Figure 34 shows an article obtained by the apparatus of figure 33.

Figure 35 shows an apparatus operated by injection fluid.

Fig. 36 and 37 show two possibilities of forming the upper surface of one layer.

FIG. 38 shows an apparatus for undercoating a curved object.

Figures 39, 40a and 40b show different articles obtained with the apparatus of the invention.

Figures 41 and 42 show articles obtained with the apparatus of the invention, which articles comprise some of the hardest areas.

Figure 43 shows an apparatus for simultaneously making a multilayer article.

Figure 44 shows another variation of an apparatus for simultaneously making a multi-layer article.

Figure 45 shows an apparatus comprising a system for injecting plastic material into a reservoir.

Fig. 46 and 47 illustrate the operation of an apparatus including an injection system.

Fig. 48 and 49 illustrate the operation of another apparatus including an injection system.

Figures 50 and 51 very schematically show a plastic material injection system for a plurality of coating apparatuses.

FIG. 52 shows a plurality of coating apparatuses using a single drive train.

Fig. 53-55 illustrate multiple coating apparatuses positioned on a single rotating system.

Figures 56 and 57 show a combination of an infusion device and a device according to the invention.

Fig. 58 shows a combination of an extrusion apparatus and an apparatus according to the invention.

FIGS. 59-62 illustrate the manufacture of a multilayer article.

Fig. 63-66 illustrate the manufacture of a multilayer article.

Detailed Description

The inventive concept is illustrated in fig. 1, 2, which schematically show a first embodiment.

A part 1 to be coated comprises a surface 6, on which surface 6 plastic material 8 in a reservoir 2 is deposited. The surface 6 to be coated, the two fixed walls 3, 4 and one wall 10 form the cavity 5 of the reservoir 2, the wall 10 being adjacent to a channel 9, the plastic material 8 flowing out of the reservoir 2 through the channel 9 to form a layer 7 of plastic material. The reservoir 2 may also comprise two side walls, not shown in fig. 1. The channel 9 is located between the wall 10 and the coated part 1. The channel 9 is characterized by a height E and a length L. When the reservoir 2 is moved relative to the coated part 1 (relative movement being effected to the right in fig. 1), the coating 7 is formed behind the channel 9. The height e of the coating 7 is determined by the gap between the wall 10 and the part 1 to be coated.

Fig. 2 is a schematic view at the channel 9. It is noted that the thickness E of the layer 7 is preferably smaller than the height E. The thickness E of the deposit depends mainly on the height E, the length L, the relative speed between the wall 10 adjacent to the channel and the coated part 1, the pressure in the cavity and the rheology of the plastic material 8.

The plastic material 8 in liquid or paste state initially fills the cavity 5. During the coating operation, the surface 6 to be coated and the reservoir 2 are moved relative to each other. Thus, with respect to the relative movement, it will be appreciated that the surface 6 to be coated may be stationary and the reservoir 2 movable, or vice versa, or that both the surface 6 to be coated and the reservoir 2 are movable. The combination of the movement of the coated part 1 and the approach of the wall 10 adjacent to the channel and of the wall 3 opposite to the wall 10 to create a pressure in the cavity 5 causes the plastic material 8 to be expelled from the cavity 5, the coated part 1 bringing the plastic material 8 by contact. In fact, more generally speaking, the pressurization of the plastic material 8 inside the cavity 5 is not entirely due to the movement of the wall 10 adjacent to the channel and of the wall 3 opposite to the wall 10, but to the movement which forms the whole wall of the cavity 5 and which makes it possible to reduce the volume of said cavity.

It is of interest to point out the advantages of the coating device according to the invention, which is intended to achieve coatings from very small to very large thicknesses with plastic materials of very different rheological properties. Thus, when the plastic material 8 is very thin or the opening is large, a small pressure (in some cases zero) in the cavity 5 can be used, the plastic material 8 being carried out only by the movement of the surface 6 to be coated. Conversely, when the plastic material 8 is very viscous or the height of the channel 9 is small, a pressure is required to expel the plastic material 8 from the cavity 5.

It is also of interest to point out the effect of different parameters on the deposition thickness. For example, the thickness E of the layer 7 shown in fig. 2 is smaller than the height E of the channel 9 for a minimum pressure in the cavity 5. The thickness E is typically greater than half the height E. Since the pressure in the cavity 5 generates a flow of plastic material 8 out of the cavity 5 which is superimposed on the flow generated by the relative movement of the surface 6 to be coated and the reservoir 2, it is possible to generate a thickness E greater than the height E by increasing the pressure in the cavity 5. The height E may adjust the deposition thickness E. The increase in height E results in a greater deposition thickness E. The length L of the channel 9 can absorb pressure fluctuations in the cavity 5 without changing the deposition thickness e. It is also necessary to point out the rheological properties of the plastic material 8, the parameters of the process such as the pressure in the cavity 5 or the deposition rate, and more generally the dependence on the design of the apparatus.

The height E of the channel 9 is not necessarily constant over the length L as shown in fig. 2. The height E may increase or decrease from the cavity 5. The height E may also vary abruptly over the length L of the channel 9, like a step, which may be used to absorb sharp changes in pressure in the cavity 5 without changing the thickness of the layer 7.

When the thickness E of the layer 7 is smaller than the height E, the length L does not necessarily determine the distance from which the layer 7 of thickness E is formed. Likewise, when the thickness E is less than E, the length L may extend above the layer 7 having a thickness E.

The operation of the device can be achieved by controlling the speed of movement or pressure. For example, the following steering modes may be employed:

the wall 10 adjacent to the passage is mobile and controls the speed;

-applying a counter-pressure on the opposite wall 3 to regulate the pressure inside the cavity 5;

another example of operation is as follows:

-controlling the speed of the coated part 1;

-controlling the pressure of the wall 10 adjacent to the channel and its opposite wall 3;

once the layer 7 is formed, an air or liquid pressure can be applied to the layer 7 in order to improve the contact between the layer 7 and the coated part 1, to avoid the layer 7 falling off or to ensure good heat removal.

Fig. 3 shows the relative movement between the different parts making up the coating apparatus shown in fig. 1, the wall 3 of the relative movement opposite the wall 10 adjacent to the channel being provided with a reference mark. The coated part 1 moves relative to the wall 3 and the plastic material 8 in the cavity 5 cannot escape from between the coated part 1 and the wall 3. The wall 3 is moved relative to the wall 10 adjacent the channel to maintain the pressure of the plastics material 8 in the cavity 5 as the cavity 5 is evacuated so as to control the thickness e of the layer 7.

Fig. 4 is a schematic view of a coating apparatus according to a second variant of the invention, but this apparatus has some similarities to the previous variant. That is why parts performing the same function are denoted by the same reference numerals. This simplification will also apply to all variants of the invention presented below.

The reservoir 2 is made up of at least a surface 6 to be coated, two fixed walls 10, 3, of which the wall 10 constitutes the wall adjacent to the channel 9, and one wall 11 that can move in a direction perpendicular to the surface 6 to be coated. The reservoir also comprises two side walls, not shown. The coated part 1 is moved relative to the fixed wall 3 with the fixed wall 3 as a reference, and the plastic material 8 in the cavity 5 cannot be discharged from between the coated part 1 and the fixed wall 3. The movable wall 11 acts like a piston and can generate a pressure in the cavity 5.

Fig. 5-9 show an example of an apparatus that can be used for manufacturing hollow plastic material articles or the inner coating of hollow articles. The device comprises two pistons 12, 13 which are opposite and can slide in the space formed by the coated part 1. A lid 20 may be added to obtain a suitably closed reservoir 2. A channel 9 is formed between the end 14 of the upper piston 12 and the coated part 1.

Figure 5 shows the loading of the plastic material 8 into the reservoir 2.

Figure 6 shows the apparatus closed and the plastics material 8 in the reservoir 2 pressurised to form a first end of an article or a coating 7.

Fig. 7 shows the formation of the coating 7 by the relative movement between the reservoir 2 and the coated part 1. During the formation of the coating 7, the lower piston 13 maintains a pressure in the cavity 5.

Fig. 8 illustrates the formation of a greater length of an article or coating. It can be noted that the amount of plastic material 8 in the cavity 5 has decreased.

Fig. 9 shows the final stage of forming the article or coating 7. As the article is formed, the plastics material 8 compressed between the ends 14, 15 of the pistons 12, 13 forms the base 22 of the article.

It should be noted over this length that the end 14 of the upper piston 12 has a smaller cross-section than the inner cross-section of the coated part 1. More precisely, the clearance between the outer edge of the end 14 of the upper piston 12 and the inner wall of the coated part 1 corresponds to the height E of the channel 9.

Instead, the cross section of the end 15 of the lower piston 13 is substantially equal to the internal cross section of the coated part 1. In all cases, the plastic material 8 cannot flow between the end 15 of the lower piston 13 and the inner wall of the coated part 1.

As shown in this example, the end 14 of the upper piston 12 has a larger cross-section than the rod of the piston 12. This arrangement provides several advantages. Once layer 7 is formed, it can greatly reduce the contact time of the upper surface of layer 7 with the walls of the reservoir adjacent to the channel, so that layer 7 can be cured without being subjected to interference friction with the walls adjacent to the channel. Further benefits can be obtained from the space created between the rod of the upper piston 12 and the layer 7 formed by injecting a gas that can push the upper piston.

To manufacture an article of thermoplastic material, the article is then at least partially cooled in the apparatus before being removed from the apparatus.

FIGS. 10-15 illustrate one example of an outer coating apparatus that may be used to manufacture thermoplastic articles. The device is formed by at least three pistons 12, 13, 16 sliding in a hollow body 23, the hollow body 23 comprising an annulus 19 in the upper part of the hollow cavity of the hollow body, the inner section of the annulus 19 being larger than the section of the upper piston 12. The opening formed between the ring 19 and the upper piston 12 constitutes the channel 9.

The lower part of the upper piston 12 is surrounded by an annular piston 16, which annular piston 16 is fixed or slides in a sealed manner around the upper piston 12.

Figure 10 shows the loading of the plastic material 8 into the reservoir 2.

Fig. 11 shows the device turned off.

Fig. 12 shows the plastic material 8 in the reservoir 2 being pressurized and forming a first end of the article around the upper piston 12. It should be noted that in this example, the end 14 of the upper piston 12 has the same section as the rod of said piston 12. The end 17 of the annular piston 16 approaches the ring 19 so that the plastic material 8 is compressed.

Fig. 13 shows that relative movement between the reservoir 2 and the upper piston 12 results in the formation of the layer 7. During the formation of layer 7, annular piston 16 maintains a pressure in cavity 5.

Figure 14 shows the article being formed over a longer length. It can be noted that the amount of plastic material in said cavity 5 has decreased.

Figure 15 shows the final stage of article formation. The plastic material compressed between the annular piston 16 and the ring 19 can remain with the article, thus forming an upper edge. In addition, this edge may be eliminated once the article is removed from the apparatus.

To produce a part of thermoplastic material, the part is then at least partially cooled in the apparatus before being removed.

Figures 16-18 show the manufacture of an article of plastic material comprising two coatings 7' and 7 "with an external coating device. The principles shown in fig. 16-18 can also be used to manufacture an article of a variety of materials (glass-plastic, aluminum-plastic, paper-plastic, plastic-plastic, etc.).

Fig. 16 shows the formation of a first layer 7' of articles of plastic material in a first coating apparatus.

Fig. 17 shows the formation of a second layer 7 "of articles of plastic material in a second coating apparatus. To do this, after the first layer 7 'has been formed in the apparatus shown in fig. 16, the article is introduced into a second apparatus, which is characterized in that the inner diameter of the ring 19 "is greater than the inner diameter of the ring 19' of the first apparatus. The second layer is then formed according to a method identical to that used for the first layer 7'.

It should be noted that the lower piston 13 can be removed once the bottom formed is sufficiently strong. This variation of the invention can be used with any of the overcoat devices defined above.

Figure 18 shows a double-layer plastic article obtained with the apparatus shown in figures 16 and 17.

Figures 19-20 illustrate the manufacture of a complex geometry article of plastic material. This article is manufactured in a first stage (fig. 19) according to the same technique as that shown in fig. 10-15 and in a second stage (fig. 20) in which the article is deformed by injecting a gas between the layer 7 and the wall of the upper piston 12 in order to adhere the layer 7 to the inner wall of the hollow body 23.

The deformation by expansion shown in fig. 20 may be performed at a temperature above the melting temperature of the thermoplastic polymer. In this case, an article similar to that obtained by extrusion blowing can be obtained. Such a process may for example realize articles of PE or PP.

Alternatively, the blow-expansion denaturation shown in FIG. 20 can be carried out at a bi-directional temperature of the polymer, i.e., after the article has been partially cooled. Biaxial stretching may be achieved by a combination of expansion and axial stretching by piston motion. For example, articles of PET or PP are available.

Fig. 21-28 show the manufacture of a hollow plastic article of multiple materials (glass-plastic, aluminum-plastic, paper-plastic, plastic-plastic, etc.) by internal coating. The principles shown in figures 21-28 can also be used to manufacture articles of multilayer plastic material.

Figure 21 shows the first material 25 in place on the outer surface of the tubular body 23. In practice, the tubular body 23 is not essential, it being used mainly if the first material 25 is soft or fragile (e.g. a membrane).

Fig. 25 shows a cross-sectional view taken along line a-a of fig. 21. Fig. 25 shows the tubular body 23 open to facilitate positioning of the first material 25.

Figure 22 shows the plastic material 8 being supplied to the apparatus and the upper piston 12 being lowered and the lid 20 being closed.

Fig. 26 shows a cross-sectional view taken along line a-a of fig. 22.

Fig. 23 shows that the coating 7 is formed on the inner surface of the first material 25 when the upper piston 12 is lowered.

Fig. 27 shows a cross-sectional view taken along line a-a of fig. 23.

Fig. 24 shows the end of the article being formed by compressing the coating material between the pistons 12, 13.

Fig. 28 shows a cross-sectional view taken along line a-a of fig. 24.

Figure 29 shows an outer coating for an elongated article 1. One part 29 may hold the elongated article 1. The two parts 3, 10, which are embedded in each other, form a cavity 5, in which cavity 5 a plastic material 8 is located. The relative movement of the pieces 3, 10 and the elongated article 1 produces a deposit 7 of plastic material 8 on the outer surface of the elongated article 1.

FIG. 30 shows the fabrication of a multi-material tube using an overcoat apparatus. The first material 25 is in place. The tube head 28 is formed by compressing the material between the tubular body 1 and the matrix 26.

Fig. 31 shows the production of a tube of plastic material with an internal coating device. The cartridge 28 and shoulder 27 are formed by compressing the material between the ends 30, 31 of the two pistons 12, 13.

Figure 32 shows the manufacture of an article of plastic material comprising a protrusion perpendicular to the coating. The cavity 32 forming the protrusion is filled when the plastic material 8 contained between the pistons 12, 13 passes. The relative movement of the pistons 12, 13 allows the pressure at which the cavities forming the protrusions are filled to be adjusted.

Fig. 33 and 34 show the production of a tube of plastic material with two lateral holding claws 33, 34 by means of an internal coating.

Fig. 33 shows the formation of a coating by compressing the material comprised between the pistons 12, 13 and filling the lateral cavities 35, 36.

Fig. 34 shows the resulting plastic material article.

Fig. 35 shows an internal coating device according to which the movement of the two parts 3, 10 in the cavity formed by the coated part 1 is generated by a liquid or a gas in the cavities 39, 40 adjacent to the reservoir 2. The pressure in the left-hand cavity 39 is greater than the pressure in the right-hand cavity 40 so as to produce a movement of the part from left to right and to form the coating 7.

Fig. 36-37 show the possible geometries of the channels 9 in order to obtain a coating 7 of constant or variable thickness.

Fig. 36 shows the geometry of an opening resulting in a coating 7 of constant thickness.

Fig. 37 shows a geometry resulting in an opening of the coating 7, the upper surface 38 of the layer 7 having striations.

Fig. 38 shows an internal coating device for curved parts, according to which the mobile walls 41, 42 forming the cavity 5 containing the plastic material 8 are spherical, the movement of which is achieved by injecting a gas or liquid in a cavity 39 adjacent to the reservoir 2.

Figure 39 shows the geometry of a plastic material article that can be obtained with the coating apparatus. The main portion 43 of the article is manufactured with a device according to the invention. The upper portion 44 of the article is manufactured separately and attached to the main portion 43.

In some cases, the main part and the upper part of the object can be manufactured in one stage in the coating apparatus.

Figures 40a and 40b show the shape of an article of plastic material that can be obtained using a variant of the method shown in figures 19 and 20.

Fig. 41 and 42 show articles realized according to the invention, whose wall thickness is not uniform.

Figure 41 shows an article of plastics material having thicker walls at an angle 45 which may reinforce the part.

Fig. 42 shows a package of plastic material, the wall thickness of which decreases along a spiral 46. The reduced thickness facilitates opening and facilitates compactness at the end of the package.

Fig. 43 shows the implementation of a multi-layer coating, with different layers deposited simultaneously. The coating device is formed by walls 10 ', 10 ", 10'" and pistons 12, 13 which are adjacent to the channels 9 ', 9 ", 9'" and which are movable relative to each other. A multilayer coating is deposited on the surface of one of the pistons 12.

Fig. 44 shows the simultaneous realization of a multilayer coating on the surface of the piece 1, the pressing of the components being applied by the movement of the walls 11 ', 11 ", 11'", respectively.

FIG. 45 shows an external coating device which can realize a discontinuous coating 7a, 47, 7b of the part 1. An extruder 48 supplies the reservoir 2 with plastic material. The movement of the closed opening of the reservoir 2 produces a discontinuous coating 7a, 47, 7 b.

Fig. 46 and 47 show the realization of an article of plastic material with an outer coating device. An extrusion system 48 provides coating material to the reservoir 2. FIG. 47 illustrates an end 50 of an article; the wall 3 is in contact in a sealed manner with the wall 10 adjacent to the channel during its movement, thus insulating the article end 50 from the plastic material.

As can be seen, FIGS. 45, 46, 47 show an overcoat apparatus with an occluder which can achieve a discontinuous coating.

Other types of occluders may be provided, for example a knife-type occluder located outside the reservoir, and preferably at the outlet of the reservoir. In the open position, the plug does not interact with the coating, thus allowing the material to flow freely from the reservoir.

The plug stops the flow of the reservoir when it is closed and may also be used to cut off the coating and form the upper end of the part.

Fig. 48 and 49 show the supply of plastic material to a coating apparatus by means of an injection press or a discontinuous extrusion system 48. Fig. 48 shows the reservoir 2 of the filling coating device. Fig. 49 shows an implementation of an article.

Fig. 50 and 51 show in a very simplified manner that several coating units 57 are fed by one single feed unit 48. The plastic material may be provided through some hot piping from the extrusion system up to the coating apparatus 57. Some occlusion ports may be used. Fig. 50 shows the feeding of four coating units through an injection press 48 and supply lines 51. Fig. 51 shows sixteen coating units 57 being fed by an injection press 48 and supply lines 51.

Fig. 52 shows eight parallel coating units 57 driven by the same schematically indicated system 52-55.

Fig. 53 and 54 illustrate a sequential manufacturing process. The coating device 57 is located on a rotary device 56 of the endless conveyor type. An extrusion system 48 provides molten material to a coating apparatus 57. Fig. 54 shows the realisation of an article of plastic material comprising several materials.

FIG. 55 shows eight groups of coating apparatuses 57, each group comprising two coating apparatuses, mounted on an endless conveyor 56. The coating equipment in each group is driven in parallel. Each group is brought in turn.

Fig. 56 and 57 illustrate the combination of the injection method and the compressive coating. The coating apparatus is located in a mold 58, 59 that forms a cavity 60. Fig. 56 shows the filling of the cavities of the moulds 58, 59 with the injection press 48. The reservoir 2 of the coating device is part of the cavity 60. Figure 57 shows a tubular element forming an article to be constructed, which may for example form part of a table. The article thus manufactured comprises at least one portion realized according to the invention. The combination of the injection method with the coating method according to the invention is particularly interesting for reducing the injection pressure and for producing complex parts with fine walls.

FIG. 58 shows a combination of an extrusion process and a coating process as described herein. An extruder 48 may produce a sheet 61 according to the flat extrusion method; an apparatus can convert the continuous advance of the sheet 61 into an intermittent advance; a heating device 62 may heat the sheet 61 to a coating temperature consistent with the present invention. This method makes it possible, for example, to produce articles of the reservoir type with a constant wall thickness and a great depth. Very thin sidewalls can be obtained.

Fig. 59 to 62 show the production of a multilayer object starting from a multilayer disk which is supplied into the reservoir by means of an inner coating.

Fig. 59 shows the supply of material 8a, 8b, 8c into the reservoir to form a multi-layer disc. One possibility to form a multi-layer disc is to provide the materials 8a, 8b, 8c successively into the reservoir. Another approach is to pre-form a multi-layered dose and provide it to the reservoir.

Fig. 60 shows the lower piston 13 raised to pressurize the material in the reservoir and form the upper portion of the article by compression. The lid 20 allows to obtain a suitably closed reservoir 2.

Fig. 61 shows the piston 12 lowered and the materials 8a, 8b, 8c forming the coating 7 on the inner surface of the tubular body 1 deformed respectively. The coating 7 consists of layers 7a, 7b, 7c corresponding to the materials 8a, 8b, 8c, respectively, provided in the reservoir.

Fig. 62 shows the resulting multilayer part. The material 8a first provided into the reservoir is located on the outer surface of the manufactured part and the material 8c last provided into the reservoir is located on the inner surface of the article. It is noted that articles comprising more than three layers may be obtained.

FIGS. 63-66 show examples of implementing a multilayer article starting from a multilayer disc provided in an overcoat apparatus.

Fig. 63 shows the supply of material 8a, 8b, 8c to the reservoir to form a multi-layer disc.

Figure 64 shows the pressurization of the material in the reservoir by the descent of the piston 12 and the pressure exerted by the annular piston 16. Fig. 64 shows the first portion of the article being formed around the end of the upper piston 12.

Fig. 65 shows the formation of a coating 7 consisting of layers 7a, 7b, 7c corresponding to materials 8a, 8b, 8c, respectively.

Fig. 66 shows the resulting multilayer article. The material 8a first provided into the reservoir is located on the outer surface of the manufactured part and the material 8c last provided into the reservoir is located on the inner surface of the article. It is noted that articles comprising more than three layers may be obtained.

Reference numeral table

1. Coated parts

2. Storage device

3. First wall of the reservoir

4. Second wall of the reservoir

5. Hollow cavity of reservoir

6. Surface to be coated

7. Layer of plastic material

8. Plastic materials in liquid or viscous state

9. Channel

10. Reservoir wall adjacent to the channel

11. Movable wall

12. First piston

13. Second piston

14. End of the first piston

15. End of the second piston

16. Annular piston

17. Lower surface of annular piston

18. Narrow region

19. Cyclic object

20. Cover for portable electronic device

21. Upper end of an article or a coating

22. Bottom of a hollow article

23. Hollow body

24. Substitute piston

25. Tubular article

26. Model (model)

27. Projecting shoulder of pipe

28. Pipe head

29. Holding part

30. End of the lower piston

31. End of the upper piston

32. Protruding cavity

33. Lateral fixing claw

34. Lateral fixing claw

35. Lateral cavity

36. Lateral cavity

37. Upper wall of the channel

38. Upper wall of the channel

39. Cavities for propelling fluids

40. Fluid-controlling cavity

41. Spherical movable wall

42. Spherical movable wall

43. The main part of the article

44. Upper part of the article

45. Rigid part

46. Rigid part

47. Discontinuous coating

48. Injection press/extruder for plastic materials

49. Plastic material injection port

50. Upper end of article

51. Feeding pipeline

52. Piston

53. Piston

54. End of piston

55. End of piston

56. Rotary conveyor

57. Coating apparatus

58. Half model

59. Half model

60. Model cavity

61. Sheet of plastic material

62. Heating device

Claims (31)

1. Method for producing a coating on a surface, starting from a plastic material (8) in liquid or viscous form, a coating (7) being produced on a surface (6), said plastic material (8) solidifying as soon as said coating (7) is formed, characterized in that the plastic material (8) in liquid or viscous form is introduced into a variable-volume reservoir (2), at least a part of the inner wall of which is formed by a part of said surface (6); -the reservoir (2) and the surface (6) are moved relative to each other while reducing the volume of the reservoir (2) in order to compress the plastic material (8) and to make the plastic material (8) flow through a channel (9), the channel (9) connecting two surface portions disposed respectively inside and outside the reservoir (2), -the flow rate of the plastic material (8) through the channel (9) being chosen in order to form a coating (7) on one of the surface (6) portions, the thickness (E) of the coating (7) being smaller than the height (E) of the channel.

2. Method according to the preceding claim, characterized in that said surface (6) is stationary and said reservoir (2) is moved.

3. A method according to claim 1, characterized in that the reservoir (2) is stationary and the surface (6) is moved.

4. Method according to any one of the preceding claims, characterized in that said layer (7) of plastic material is deposited on the inner wall of a hollow body (1), said reservoir (2) being formed by the ends (14, 15) of two pistons (12, 13) sliding in said hollow body (1) and opposed to each other, and by a portion of the inner wall of said hollow body (1).

5. The method according to claim 4 for producing a coating on the inner wall of a hollow body (1), characterized in that the coating is fixed to the inner wall of the hollow body (1).

6. A method as claimed in claim 4, for manufacturing a tubular element, wherein said layer (7) is formed separately from said tubular body (1).

7. A method according to any one of the preceding claims, wherein said layer (7) of plastic material is deposited on the outer wall of a tubular body (1, 12) by means of a reservoir (2), said reservoir (2) surrounding an annular portion of the outer wall of said tubular body (1, 12) and sliding with respect to said tubular body (1, 12).

8. A method according to claim 7, characterized in that after said layer (7) has been deposited, a fluid is injected between said layer (7) and the outer wall of said tubular body (1, 12) to separate said layer (7) from said tubular body (1, 12) and away from said tubular body (1, 12).

9. A method as claimed in any one of the foregoing claims, characterized in that the plastic material (8) is injected into the reservoir (2) while the reservoir (2) is relatively moved; and increasing the volume of the reservoir (2) before or simultaneously with the deposition of the plastic material (8).

10. The method of any of the preceding claims, in combination with a method of producing at least one coating by compression.

11. The method of any of the preceding claims, in combination with a method of producing at least one coating by injection.

12. The method of any of the preceding claims, in combination with a method of producing at least one coating layer by extrusion.

13. Apparatus for producing a coating on a surface, the method according to claim 1 being carried out to produce a coating on a surface, characterized in that the apparatus comprises:

-a surface (6) to be coated;

-a reservoir (2) of variable volume, at least a portion of the inner wall of which is formed by a portion of said surface (6);

-a channel (9) connecting the two surface (6) portions respectively arranged inside and outside the reservoir (2), the height (E) of said channel constituting an upper limit for the thickness (E) of a coating (7) to be deposited;

-means (12, 13) for effecting the movement of said reservoir (2) with respect to said surface (6);

-means (10) for reducing the volume of said reservoir (2) when it is moved relative to each other.

14. The apparatus of claim 13 in combination with an apparatus for producing at least one coating by compression;

15. the apparatus of claim 13 or 14 in combination with an apparatus for producing at least one coating by injection.

16. Apparatus according to any one of claims 13 to 15 in combination with an apparatus for producing at least one coating by extrusion.

17. The apparatus according to any one of claims 13 to 16, additionally comprising a plastic material injection device (48).

18. The device according to any one of claims 13 to 17, characterized in that said surface (6) is stationary and said reservoir (2) is movable.

19. The device according to any one of claims 13 to 17, characterized in that said surface (6) is mobile and said reservoir (2) is fixed.

20. The apparatus according to any of the foregoing claims from 13 to 19, characterised in that the reservoir (2) is formed by the inner wall of a hollow body (1, 23) and the ends (14, 15, 17) of two pistons (12, 13, 16) opposite each other, sliding in the hollow body (1, 23).

21. Apparatus according to any one of claims 13 to 20, comprising means for injecting a fluid between said coating layer (7) and said surface to be coated (6) in order to separate said coating layer (7) from said surface to be coated (6).

22. An apparatus as claimed in any one of claims 13 to 21, comprising means (48) for injecting said plastic material into said variable-volume reservoir.

23. The apparatus according to any one of claims 13 to 22, comprising a plurality of variable-volume reservoirs (2) distributed in sequence along the surface to be coated (6).

24. The device according to any one of claims 13 to 23, comprising a plurality of variable-volume reservoirs (2) distributed in an adjacent manner.

25. An apparatus as claimed in any one of claims 13 to 24, characterized in that said surface to be coated (6) comprises a cavity for receiving said plastic material (8).

26. Plant according to any one of claims 13 to 25, characterized in that it communicates with a device (48) for providing plastic material.

27. Plant as in any claim from 13 to 26, characterized in that said plant is carried by the same system (52-55).

28. The plant according to any one of claims 13 to 27, characterized in that the plant is part of a rotary system (56), the rotary system (56) being able to treat each article in turn.

29. Article obtained by the method according to any one of claims 1 to 12, characterized in that it comprises a coating of plastic material, initially in liquid or viscous form, which, once deposited, solidifies, the inner and outer surfaces of said layer having different roughness.

30. The article of claim 29, comprising a layer of variable thickness.

31. An article according to claim 29 or 30, comprising at least one protrusion of plastic material along one of the walls of the article.