DE2544042A1 - METHOD AND DEVICE FOR MANUFACTURING THIN-WALLED ARTICLES FROM PLASTIC - Google Patents

Description

Patent attorney
Dipl.-Ing. Waiter Jacklsoh

7 Stuttgart N, Msnzelstrasse & Q

Plastona (John. Waddington) Limited A Jh 97 ^ - Re Wakefield Road

Leeds LSIo 3TP, Yorkshire

England 1st October 1975

Method and device for the production of thin-walled objects from plastic

The invention relates to a method of manufacture thin-walled objects made of plastic by deforming a strip-shaped or plate-shaped plastic material, in which it can be laminates.

Any suitable technique, such as B. the deformation under vacuum, under pressure, with the help of bolts or mechanical deformation or any combination of the said techniques can be used in the manufacture of the articles in question. All manufacturing processes mentioned are the common feature that the starting material must be heated in order to be able to soften the same to a degree, that it can be deformed. For this reason, when deforming such objects, one speaks simply and generally from "thermoplastic deformation".

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Thermoplastic deformation of plastic is, of course, well known and widely used; and it are many made by thermoplastic deformation Articles for everyday use in many countries around the world, including household dishes Drinking cups is intended.

Certain materials, especially polypropylene, polyethylene and cellular plastic sheets invent very precise temperatures for thermoplastic deformation in order to to achieve high-speed production and, at the same time, a high quality of the products produced. Conventional Methods of heating the starting material, such as infrared heaters, do not ensure sufficient Accuracy of the heating process in order to achieve the mentioned desirable properties of the production process or of the finished products to achieve. This is not possible even if the starting material is to be thermoplastically deformed has a uniform thickness, which is usually not the case in commercial practice.

If the heating is carried out by applying radiant heat, there is a further disadvantage that Many types of plastic sheets wrinkle or sag or sag under the influence of heat, which in turn cause further temperature differences in the heated plastic plate.

The object of the present invention is to provide a heating method to find which one for a very wide range

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sheet-shaped plastic material is suitable, including such materials as polystyrene, A.B.S. Acrylonitrile, Nylon, polyester, polyvinyl chloride, cellulose acetate, the so-called "filled" plastic material, which is made of plastic and a special inorganic filler. The heating method according to the invention should moreover for every thermoplastically deformable sheet-shaped plastic material be suitable and avoid or at least reduce the disadvantages of known methods described above.

According to the basic idea of the invention, the problem essentially becomes solved in that the objects by thermoplastic deformation from a heated strip-shaped plastic material are produced and the tape-shaped plastic material heated by being around heated rollers Walken is diverted.

The heating of the strip-shaped material is ensured by contact with the heated rollers and hot gas and / or steam even a heating of the tape material over its entire width, and the tape material cannot at any point Reach temperature that is above the temperature of the rollers or or the gas and / or steam goes out.

The strip material can be passed through a chamber, which the rollers' and corresponding gas and / or Contains fluid media.

The band material is preferably designed to be endless directly fed to a machine for thermoplastic deformation, in which the objects are formed and the

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drive will be repeated. Of course it plays for them present invention does not matter what construction it is in the articles to be manufactured in detail acts.

Preferably, the strip-shaped material moves both into and out of the chamber in one horizontal direction and in the same plane, and the RoI-lenführungunq can . have three rollers each with horizontal axes, with two of the rollers above the third Roll and are arranged symmetrically to the vertical plane running through them. Any role is preferred heated by hot oil circulating within it.

The strip material first moves over and around one of the two upper rollers, then runs over the lower roller and is then passed around again over the other upper roller, in such a way that a course results at dm. said vertical plane forms the axis of symmetry. The rollers are preferably sized and arranged so that, as the strip material moves through the chamber, it is in uniform contact with the rollers on each of its two surfaces.

Inlet and outlet means can be provided through which a gaseous and / or vaporous medium enters the chambers initiated or removed from these again. The temperature of the rollers and the gaseous and / or vaporous medium is preferably precisely controlled in such a way that the strip material is set to a uniform, precise temperature

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is heated, preferably to a temperature that allows an immediately subsequent thermoplastic deformation of the strip material permitted.

The temperature of the rollers and of the gas and / or vaporous medium can preferably be controlled in a thermostatic manner in order to to make sure that the tape material is kept at a critical temperature. The minimum of the length of time during which the material to be deformed must stay inside the chamber in order to reach the desired temperature, is of the Dimensions of the tape material depend on. In any case, however, this time can be set to suit the material to be heated to be adjusted. For a maximum heating time does not need to be taken into account because the temperature of the strip material can never be higher than the temperature inside the chamber.

Objects, such as household dishes made of polypropylene, which are heated in the manner described above, can be reliable be manufactured in large numbers. If you look at the average of a large number of individual pieces, thus the objects have an excellent surface quality, strength and clarity, which properties are the characteristics that of conventionally molded polypropylene articles.

Since the deformation machine "· works on a cyclical basis, with a dwell time of the to be deformed Objects or a one-off filling with these is required, it is useful if accordingly

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for
also the strip material is cyclically provided with a dwell time with regard to its contact with the rollers.

It is not necessary that the heating caused by the The entire heating process of the tape

that material represents. Rather, it is entirely possible / pre- and / or post-heating, e.g. by heating steam, radiation Or the like., Can be provided. These additional heating processes may appear suitable when the tape material to be heated is polystyrene, So the heating chamber could serve to carry out the main part of the heating process, while e.g. conventional Radiant heaters, which would be well suited for the main heating process, only for a small reheating process could be used to change the strip material from the temperature at which it leaves the liquid bath to the deformation temperature bring to. In any case, however, there is contact of the strip material with the "rollers" and the heating Always useful in the gas and / or vapor-free medium in the heating chamber because of the even temperature distribution, which is thereby · achieved.

By the invention a simple process is provided whereby a plastic material in strip form in a uniform manner can be heated and thereby is able, in an effective manner plastics, such as polyolefins, z * B ■ polypropylene, for producing articles to be used by thermoplastic means and in large numbers. The one used to manufacture the items

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required working period can be kept very short due to the method according to the invention, and in many In some cases, this makes it possible to produce these articles at lower cost with higher quality at the same time.

The invention also includes the subject matter obtained by the above-explained method according to the invention have been manufactured.

According to a further feature of the invention is eire for Manufacture of thin-walled objects made of plastic usable device characterized by means for delimiting a heating chamber, outlet and inlet means, through which a tape-shaped plastic material in the Chamber can be guided in or out of this, roller means around which the strip-shaped plastic material means for heating the roller means .; and inlet and outlet means through which hot gaseous and / or vaporous agents can be introduced into said chamber or removed from it.

In the drawing is an embodiment of the invention shown and described below. The drawing shows schematically a heating chamber in partial side view.

According to the drawing, the heating chamber is formed by a housing with a front wall lo, rear wall 12 and a base 16 and a cover 14. Furthermore, the housing has two side walls, of which only the side wall designated by 18

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is shown because the drawing is a side view. The front wall Io shows in its uppermost area an entry slot 2o, whereas the rear wall 12 is provided with an exit slot 22. the Slots 2o, 22 are arranged in alignment with one another in the horizontal direction and allow a passage to pass through thermoplastically deformable tape material 24, e.g. Polypropylene, so that the bandraateri al 24 into the heating chamber the slot 2o enters and comes out of this again through the slot 22.

Front wall Io and rear wall 12 also have inlets 2.6 for a gaseous and / or vaporous heating medium. In the example described, the heating medium is air. When the heating chamber is in operation, heated air is continuously introduced into the heating chamber through the inlets 26. For the subsequent removal of the air from the heating chamber, extraction tubes 28 are used, which - as can be seen from the drawing - are each arranged above and below the inlet slot 2o and outlet slot 22.

Inside the heating chamber are three heated rollers J5o, and 34 arranged. The axes of these roles lie to one another parallel and are directed horizontally, and the rollers Jo and 32 are in a higher position than the roller 34. The arrangement is made so that the roles 3o and 32 are symmetrical to a vertical plane, the goes through the axis of the roller 34. The rollers are heated

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by heated oil, which is inside the cavities of the Rolls circulated. In order to achieve good heat transfer from the roller surfaces to the strip material 24, the surfaces of the rollers 3o, 32 and 34 are made of metal, manufactured. After the strip material 24 infrared preheater 36 has happened, it moves - as shown - over the roller 30 is then guided around the roller 34 and then moves over roller 32. Eventually the strip material 24 leaves the heating chamber through the exit slot 22, and it can be seen from the drawing that the heating chamber is entering Strand of the strip material and the strand emerging therefrom in relation to the Heizkaramer in one and the same horizontal plane.

The temperatures of the rollers and the ambient temperature inside the heating chamber will be within precise limits held to ensure that the tape material 24 is heated to a uniform and proper temperature. The strip material is thus prepared for direct transfer from the outlet slot 22 of a machine to the thermoplastic Deformation to be fed, in which the objects are made from the strip material. The temperatures mentioned are controlled by the circulation of both the hot air inside the heating chamber and the oil from the heating rollers 30, 32 and 34, with suitable thermostats provided in order to keep the temperatures within precise limits, for example the air flowing through the inlets 26 in the heating chamber is initiated, have a temperature of 160 ° C for polypropylene material, and the rollers 30,

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would be kept at a similar temperature.

The dimensions and the arrangement of the rollers 3o, 32 and 34 are preferably chosen so that - while the strip material 24 runs over the reels - on each side of the banl materials, there is always the same contact area between the rollers and the strip material. For this purpose it can be recommended the roles 3o, 32 and 34 with slightly higher To run speeds to compensate for any elongation of the strip material 24 during of the heating process can take place, and to ensure that the strip material 24 is in egem contact with the roles remains. It is also possible to arrange the rollers 3o, 34 and 32 so that between the rollers 3o and 34 on the one hand and between the rollers 34 and 32 on the other hand a nip is formed in each case in order to guide the strip material 24 through the heating chamber cause or support.

While the device described above is the preferred embodiment of the invention, should nevertheless be pointed out that modifications of this preferred embodiment are conceivable without leaving the scope of the invention. For example, it would be possible to provide a device that only two Rolls includes, wherein the strip material is moved in S-formation around these rollers and with a uniform Belt material is used to make contact with the rollers on either side thereof. Further it is conceivable that the heating chamber has suitable baffles

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contains to ensure that the hot air which is introduced into the chamber, is directed towards the rollers.

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Claims (14)

Patent Attorney Ä 25 Uk - 12 - Plastona (John Waddington) Limited A 34 974 - Re 1st October 1975 Expectations : Process for the production of thin-walled objects made of plastic, characterized in that the objects be produced by thermoplastic deformation from a heated strip-shaped plastic material and the strip-shaped plastic material is heated by passing it around heated rollers. 2. Verßthren according to claim 1, characterized in that the strip-shaped plastic material is introduced into and out of a heating chamber, and that the heating chamber a gaseous and / or liquid medium contains. 3. The method according to claim 2, characterized in that the strip-shaped plastic material moves into and out of the heating chamber in a horizontal direction Direction and moved in the same plane. 5 609816/0789 4. The method according to claim 3, characterized in that the RollefuVnrung consists of three rollers whose axes are parallel to each other, two of the rollers are arranged above the third roller and symmetrically to * a vertical plane passing through the third roller, and that the strip-shaped plastic material moves over and around one of the upper rollers, then guided around the lower roller and finally moved over the other roller, in such a way that a movement is created which has the said vertical plane as the axis of symmetry. 5. The method according to claim 4, characterized in that that the rollers have such dimensions and are arranged so that the band-shaped plastic material - as it moves through the heating chamber - uniform contact with the Has rollers on each of its two surfaces. 6. The method according to claim 4 or 5, characterized in that each roller is heated by hot oil circulating within it. 7. The method according to claim 6, characterized in that the temperature of the circulating in each roll Oil is monitored thermostatically, so that each roll is kept at a preselected constant temperature. - 14 609816/0789 8. The method according to any one of claims 2 to 7, characterized in that the temperature of the gas and / or Vaporous medium is monitored thermostatically, so that it is on a preselected constant value is kept » 9. The method according to claim 8, characterized in that air is used as the gaseous medium in the heating chamber. 10. The method according to any one of claims 2 to 9 * characterized in that the gaseous and / or vaporous medium circulates within the heating chamber. 11. The method according to any one of the preceding claims, characterized in that the strip-shaped plastic material directly from the heating by the rollers and by the gaseous and / or vaporous medium reaches the machine for thermoplastic deformation. - 15 - 609816/0789 12. Device for use in the manufacture of thin-walled objects made of plastic, characterized by means of delimiting a heating chamber, exclusion, step and entry means through which a strip-shaped plastic material is fed into the heating chamber or out of this again ^ conducts noise, roller means around which the strip-shaped plastic material means for heating the roller means, as well as inlet and outlet means, through the hot gaseous and / or vaporous Agents can be introduced into said heating chamber or removed from it. 13. The apparatus according to claim 12, characterized in that the roller means consists of three rollers, each with a horizontal Axis consist, with two of the rollers above the third roller and symmetrical about one through the vertical plane passing through the third roller, and that exit and entry means are arranged so that the strip-shaped plastic material in the heating chamber · and out of this again can be moved out in the horizontal direction and in one and the same plane, and the band-shaped Plastic material inside the heater initially over and over one of the two upper rollers is passed around this, then passed around the lower roller and finally over the upper roller is, in such a way that a course of the band-shaped plastic material is produced, which said Has vertical plane as an axis of symmetry. - 16 609816/0789 14. Apparatus according to claim 12 or 13, characterized in that that the same with a machine for the thermoplastic deformation of the strip-shaped plastic material combined and arranged in such a way / that the heated strip-shaped plastic material of the heating device goes directly to the machine for thermoplastic deformation » 609816/0789