FR2646123A1 - Method of manufacturing a hollow thermoplastic article and article obtained thereby - Google Patents
Method of manufacturing a hollow thermoplastic article and article obtained thereby Download PDFInfo
- Publication number
- FR2646123A1 FR2646123A1 FR8905938A FR8905938A FR2646123A1 FR 2646123 A1 FR2646123 A1 FR 2646123A1 FR 8905938 A FR8905938 A FR 8905938A FR 8905938 A FR8905938 A FR 8905938A FR 2646123 A1 FR2646123 A1 FR 2646123A1
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- FR
- France
- Prior art keywords
- mold
- article
- manufacturing
- walls
- crosslinked
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
- B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
- B29C41/20—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. moulding inserts or for coating articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/12—Moulds or cores; Details thereof or accessories therefor with incorporated means for positioning inserts, e.g. labels
- B29C33/123—Moulds or cores; Details thereof or accessories therefor with incorporated means for positioning inserts, e.g. labels for centering the inserts
- B29C33/126—Moulds or cores; Details thereof or accessories therefor with incorporated means for positioning inserts, e.g. labels for centering the inserts using centering means forming part of the insert
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
- B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
- B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Moulding By Coating Moulds (AREA)
Abstract
Description
PROCEDE DE FABRICATION D'UN OBJET CREUX
EN MATIERE THERMOPLASTIQUE ET OBJET AINSI OBTENU
Le présente invention intéresse l'industrie des matières plastiques et concerne plus particulièrement les techniques de rotomoulage mises en oeuvre dans cette industrie.PROCESS FOR MANUFACTURING A HOLLOW OBJECT
IN THERMOPLASTIC MATERIAL AND OBJECT THUS OBTAINED
The present invention is of interest to the plastics industry and relates more particularly to the rotational molding techniques used in this industry.
Sommairement, le rotomoulage consiste à introduire une quantité déterminée d'une matière thermoplastique, se présentant généralement à l'état de poudre, dans un moule ayant la forme d'un objet donné et entraîné en rotation selon deux axes orthogonaux, à chauffer ledit moule pendant sa rotation et à refroidir ce dernier pour obtenir ledit objet. Briefly, rotational molding consists of introducing a determined quantity of a thermoplastic material, generally in the powder state, into a mold having the shape of a given object and driven in rotation along two orthogonal axes, to heat said mold during its rotation and cooling the latter to obtain said object.
Le problème qui se pose avec les objets creux ainsi réalisés réside dans l'insuffisance de l'épaisseur de leurs parois en certains endroits où les contraintes mécaniques sont les plus importantes et notamment dans les zones adjacentes aux percées, ces zones ayant en effet tendance à se déformer avec le temps. The problem which arises with the hollow objects thus produced lies in the insufficiency of the thickness of their walls in certain places where the mechanical stresses are the greatest, and in particular in the zones adjacent to the breakthroughs, these zones having in fact a tendency to distort over time.
Pour résoudre ce problème, il est nécessaire d'obtenir une épaisseur de parois plus importante aux endroits critiques et pour ce faire, de chauffer de manière sélective les différentes parties des parois du moule de façon à attraire une plus grande quantité de matière thermoplastique aux points où la température est la plus élevée. Cependant, dans la pratique on constate que la matière qui s'agglomére ainsi aux points les plus chauds, a tendance, en raison de sa grande fluidité, à s'écouler le long des parois du moule avant de se figer. Il en résulte que les parois de l'objet ainsi moulé ne présentent pas uniformément l'épaisseur adéquate recherchée. To solve this problem, it is necessary to obtain a greater wall thickness at the critical points and to do this, to selectively heat the different parts of the walls of the mold so as to attract a greater quantity of thermoplastic material at the points. where the temperature is the highest. However, in practice it is found that the material which thus agglomerates at the hottest points, tends, due to its great fluidity, to flow along the walls of the mold before freezing. As a result, the walls of the object thus molded do not uniformly have the desired adequate thickness.
Le procédé de fabrication, objet de la présente invention, constitue une solution à ce problème, à la fois économique et simple à mettre en oeuvre. The manufacturing process, object of the present invention, constitutes a solution to this problem, which is both economical and simple to implement.
L'invention vise également les objets réalisés avec ce procédé.The invention also relates to the objects produced with this method.
Plus précisément, I'invention concerne un procédé de fabrication d'un objet creux en matière thermoplastique, ledit procédé consistant à introduire une quantité déterminée de ladite matière dans un moule rotatif, à chauffer ledit moule pendant sa rotation et à refroidir ledit moule pour obtenir ledit objet, ce procédé étant remarquable en ce que, préalablement à l'introduction de ladite matière, une couche au moins d'un matériau réticulé est disposée à proximité des parois internes dudit moule. More specifically, the invention relates to a method of manufacturing a hollow object made of thermoplastic material, said method consisting in introducing a determined quantity of said material into a rotary mold, in heating said mold during its rotation and in cooling said mold to obtain said object, this method being remarkable in that, prior to the introduction of said material, at least one layer of a crosslinked material is disposed near the internal walls of said mold.
Selon un mode de mise en oeuvre du procédé de l'invention, ce matériau réticulé sera constitué par un treillis, par exemple métallique ou textile. According to an embodiment of the method of the invention, this crosslinked material will consist of a mesh, for example metallic or textile.
Un tel matériau sera, en fonction de l'importance et de la localisation des contraintes subies par l'objet moulé, disposé dans des zones déterminées du moule et plus particulièrement dans les zones où seront ménagées des ouvertures dans la paroi dudit objet. Depending on the size and location of the stresses to which the molded object is subjected, such a material will be placed in specific areas of the mold and more particularly in the areas where openings will be made in the wall of said object.
On comprend parfaitement que la configuration réticulaire d'un tel matériau, permet de limiter l'écoulement de la matière thermoplastique lors de sa fusion sans entraver son dépôt sur les parois du moule. En effet, la poudre de matière thermoplastique introduite dans le moule après la mise en place du matériau réticulé, pourra venir en contact avec les parois dudit moule en passant au travers des mailles dudit matériau. Ce dernier, après le commencement des opérations de rotomoulage, servira alors en quelque sorte de support à ladite matière se trouvant, selon son degré de température, dans un état mi-pâteux mi-liquide. It is perfectly understood that the reticular configuration of such a material makes it possible to limit the flow of the thermoplastic material during its melting without hindering its deposition on the walls of the mold. In fact, the powder of thermoplastic material introduced into the mold after the setting of the crosslinked material, may come into contact with the walls of said mold by passing through the meshes of said material. The latter, after the beginning of rotational molding operations, will then serve as a kind of support for said material being, depending on its temperature, in a semi-pasty semi-liquid state.
Comme précisé ci-dessus, le matériau réticulé doit être positionné à proximité des parois internes du moule, autrement dit ne pas se trouver en contact étroit avec ces dernières, ceci afin de permettre à la matière thermoplastique de l'envelopper totalement. Pour ce faire, ledit matériau comporte des moyens de cale qui offrent un appui sur les parois du moule sans autoriser un contact total avec celles-ci. De tels moyens de cale pourront être constitués par les pièces amovibles associées aux parois du moule et destinées à la réservation des ouvertures dans les parois de l'objet moulé ou plus simplement encore, et notamment dans les zones dépourvues de telles pièces, par des noeuds faisant saillie sur la surface dudit matériau.Dans ce dernier cas, la rigidité relative de ce matériau, qui peut être constitué comme celà a été dit par un treillis métallique, lui permettra d'être maintenu en place à l'intérieur du moule. As specified above, the crosslinked material must be positioned near the internal walls of the mold, in other words not be in close contact with the latter, this in order to allow the thermoplastic material to completely envelop it. To do this, said material includes wedge means which provide support on the walls of the mold without allowing total contact with them. Such shim means may be constituted by the removable parts associated with the walls of the mold and intended for the reservation of the openings in the walls of the molded object or more simply still, and in particular in the areas devoid of such parts, by nodes. protruding from the surface of said material. In the latter case, the relative rigidity of this material, which can be made as has been said by a wire mesh, will allow it to be held in place inside the mold.
De préférence, ces noeuds saillants seront réalisés dans une matière fusible, par exemple une matière plastique, de manière à disparaître lors des opérations de rotomoulage et à ne pas former ainsi d'éventuelles aspérités affleurant sur l'objet moulé. Preferably, these protruding nodes will be made of a fusible material, for example a plastic material, so as to disappear during rotational molding operations and thus not to form any rough edges which are flush with the molded object.
Les dessins annexés fournissent une illustration d'un matériau réticulé susceptible d'être utilisé avec le procédé de fabrication de l'invention, cette illustration et le commentaire qui l'accompagne étant donnés à titre de simple exemple sans aucun caractère limitatif. The accompanying drawings provide an illustration of a crosslinked material capable of being used with the manufacturing process of the invention, this illustration and the commentary which accompanies it being given by way of simple example without any limiting character.
Ainsi qu'on peut le voir sur la Figure unique de ces dessins, le matériau réticulé est constitué d'un grillage dont les mailles sont définies par cinq fils I,..., 5 5 reliés entre eux par des noeuds 6 qui font saillie sur la surface de la couche de grillage et qui permettront de rehausser l'ensemble par rapport à la surface interne du moule. As can be seen in the single figure of these drawings, the crosslinked material consists of a mesh, the meshes of which are defined by five wires I, ..., 5 5 connected together by nodes 6 which protrude on the surface of the mesh layer and which will make it possible to raise the assembly relative to the internal surface of the mold.
Dans un mode de réalisation non illustré, on pourrait disposer deux couches de grillages superposées, l'un présentant des mailles plus importantes que l'autre, ce dernier devant être placé le plus près des parois internes du moule afin de retenir la matière thermoplastique et le premier offrant la rigidité nécessaire à l'ensemble. Ces deux couches de grillage pourront être étroitement solidarisées. Toutefois, selon les besoins et notamment selon l'importance de l'épaisseur des parois de l'objet moulé, il sera possible de disposer les différentes couches de grillage en ménageant un espace entre elles, espace où la matière thermoplastique viendra librement se solidifier. In an embodiment not shown, two layers of superimposed screens could be placed, one having larger meshes than the other, the latter having to be placed as close as possible to the internal walls of the mold in order to retain the thermoplastic material and the first offering the rigidity necessary for the whole. These two layers of mesh can be closely joined. However, as required and in particular according to the importance of the thickness of the walls of the molded object, it will be possible to arrange the different layers of mesh by providing a space between them, a space where the thermoplastic material will freely solidify.
En dernier lieu, on comprendra aisément que les parois de l'objet, dans lesquelles le matériau dont un exemple vient d'être donné se trouvera noyé, se verront renforcées ce qui constitue un autre avantage du procédé de l'invention. Finally, it will be readily understood that the walls of the object, in which the material, an example of which has just been given, will be embedded, will be reinforced, which constitutes another advantage of the process of the invention.
Claims (7)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8905938A FR2646123A1 (en) | 1989-04-25 | 1989-04-25 | Method of manufacturing a hollow thermoplastic article and article obtained thereby |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8905938A FR2646123A1 (en) | 1989-04-25 | 1989-04-25 | Method of manufacturing a hollow thermoplastic article and article obtained thereby |
Publications (1)
Publication Number | Publication Date |
---|---|
FR2646123A1 true FR2646123A1 (en) | 1990-10-26 |
Family
ID=9381415
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
FR8905938A Pending FR2646123A1 (en) | 1989-04-25 | 1989-04-25 | Method of manufacturing a hollow thermoplastic article and article obtained thereby |
Country Status (1)
Country | Link |
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FR (1) | FR2646123A1 (en) |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1592671A (en) * | 1925-10-16 | 1926-07-13 | Clifford R Nichols | Means for positioning reenforcements within molds for making bodies of plastic material |
DE1926204A1 (en) * | 1969-05-22 | 1970-11-26 | Dynamit Nobel Ag | Rotation moulding process |
DE1704381A1 (en) * | 1968-02-28 | 1971-06-16 | Thermovox Gmbh | Rotational casting process and device for the production of hollow bodies and open molded parts from plastics, and containers and molded parts produced in this way |
DE2637683A1 (en) * | 1976-08-20 | 1978-02-23 | Kabel Metallwerke Ghh | Casting thermosetting resin(s) with metal reinforcement - by inserting uniformly perforated metal tube in mould and centrifuging |
GB1530121A (en) * | 1975-10-23 | 1978-10-25 | British Industrial Plastics | Rotational moulding of plastics articles |
US4357293A (en) * | 1979-10-22 | 1982-11-02 | Williamson Jr James H | Method for molding a mounting member in place |
-
1989
- 1989-04-25 FR FR8905938A patent/FR2646123A1/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1592671A (en) * | 1925-10-16 | 1926-07-13 | Clifford R Nichols | Means for positioning reenforcements within molds for making bodies of plastic material |
DE1704381A1 (en) * | 1968-02-28 | 1971-06-16 | Thermovox Gmbh | Rotational casting process and device for the production of hollow bodies and open molded parts from plastics, and containers and molded parts produced in this way |
DE1926204A1 (en) * | 1969-05-22 | 1970-11-26 | Dynamit Nobel Ag | Rotation moulding process |
GB1530121A (en) * | 1975-10-23 | 1978-10-25 | British Industrial Plastics | Rotational moulding of plastics articles |
DE2637683A1 (en) * | 1976-08-20 | 1978-02-23 | Kabel Metallwerke Ghh | Casting thermosetting resin(s) with metal reinforcement - by inserting uniformly perforated metal tube in mould and centrifuging |
US4357293A (en) * | 1979-10-22 | 1982-11-02 | Williamson Jr James H | Method for molding a mounting member in place |
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