MXPA96005643A - Method and device to produce a mold plastic article - Google Patents

Abstract

The present invention relates to a method for producing a molded plastic article. Individual portions of material are removed from a flow of heat-plasticized material, which flows vertically downward from a dosable, dosing opening of a dispenser, and is transferred to a mold before being compressed by closing the mold for form a molded article. The required portions are cut by cutting blades of the material flow at a point below the dosing opening and at a distance from it, the flow preferably being briefly stopped for this purpose. The invention also relates to a device for the production of a molded plastic article, which comprises a lockable mold (8), and a material dispenser (1) for heat-plasticized synthetic material, which can be configured above the molding chamber (8), the dispenser has a metering opening pointing towards the mold (8), and can be closed by a closing unit (6), and from where the flow (12) of plasticized material arises . According to the invention, a cutting device (9) is located to separate the required portions (14) of material, below and at a distance from the dosed opening

Description

METHOD AND DEVICES TO PRODUCE A MOLDED PLASTIC ARTICLE The invention relates to a process and devices for producing an article molded from plastic, by separating individual portions of the material, from a downwardly directed material flow that exits from a sealable metering opening of a * ') material doser, this plastic material being heat-plasticized, transferring the separated portions of material into a hollow mold space, and compressing to a molded article upon closing the hollow mold space. This process and this device are known from the German Patent Number DE-C3-30, 23, 415. According to this process and this device, preforms are obtained in the form of a ring by separating portions of individual materials, and closing a tubular part of the material dispenser, addressing this part against the hollow space of the mold, by means of a closing element that can be displaced against the end of the tubular part in the axial direction, whereby, the portions of material in separate ring shape, are transferred by free fall into the hollow space of the mold . In relation to this, the portions of ring-shaped material are molded into preforms, by controlling the closure element, these preforms having a profile of approximately lientiform cross-section. Preferably, the ring-shaped preforins are separated from the closure element by a gas stream directed against the separation point. This process requires a complicated nozzle system which, in addition, requires a specific closure feature in order to obtain the desired cross-sectional shape of the ring-shaped preform. As. thermoplastics exhibit strong adhesive or adhesion properties, additional measures are required, as a rule, such as hot air streams to separate the produced preform from the closure device. Another process and another device are known from the European Patent Number EP-B1-328, 096. In connection with this, a preform is dosed from a nozzle, and is separated, whereby, all the heated thermoplastic material required for a preform is deposited on an intermediate carrier, which can be driven under a nozzle, the surface of the carrier forming a part of the pressure mold. Before or during mold closing, the intermediate carrier is lowered, and the preform is transferred to the pressure mold in this manner. With this device, the pressure mold is more complicated, on account of the extensible intermediate carrier, and consequently, also more expensive. According to the process according to German Patent Number DE-C3-30, 23, 415, only preforms in the form of a ring can be produced. Confoi my dad with the European Patent Number EP-B1-325, 096. The preforms can also have a ring shape. In relation to the manufacture of molded articles in the form of a tube that has to have a closed metering opening, for example, a pierceable diaphragm, or in the case of so-called "twisting" or "breaking" tubes, in relation to with which the dosing opening is released only after a properly designed closure part has been twisted and / or broken, the use of ring-shaped preforins to problems, because often inclusions occur in the form of Bubble during the pressure, causing rejections. The problem of the invention is to propose a process and a device by means of which portions of specially closed material of a desired size can be obtained in a simple and fast manner, without additional measures, as well as proposing a device by means of which tab icar portions of material desired, and particularly closed portions of material, in a simple way, having these portions a simple structure. In addition, the process and the device allow the manufacture of tubes without burrs, with an initially closed dosing opening. This problem is solved by the process with the features of claim 1, as well as by devices with the characteristics of claims 5 or 6. Preferred dopments of the process are discussed in dependent claims 2 to 7, and the preferred embodiments of the devices, in claim 7. The invention is explained in greater detail in the following, on an exemplified embodiment with the indication of the variations, as well as with reference to the drawings, in which: Figure 1 shows a schematic view of a device according to the invention, in which a flow of material flows through the open dosing opening of a material dosing device. Figures 2 to 5 show the same as Figure 1, and yet, in the form of different stages of the process, in the formation of a desired portion of material. A material doser 1 is fed by means of an extruder screw 2, with the heat-plasticized plastic 3. The material dispenser 1 has a dispensing mezzanine 5 at its bottom 4. In the material dispenser 1, a body is configured 6, it being possible to move the body upwards and downwards, and designed in such a way that its lower end 7 in an upper position (liquta 1), releases the dosing opening 5 for dosing the plastic sheet 3; that is, it closes the metered opening to 5 in a medium lowered position (Figure 2); and in a lower position (Figures 3, 4), extends from the material dispenser 3 e the direction of a hollow mold space of a pressure mold pair 8 ', which may have any known shape, also in a multi-part shape (the counter-mold is not shown), the hollow space of the mold 8 being able to be configured under the material doser 1. Between the pressure mold part 8 'and the bottom 4 of the material dispenser 1, it forms a cutting device 9, whose leaves 10 are movably configured, and are capable of moving against and away from one another, in such a way that their cutting edges 11 slightly overlap one with the other at the end of an operation of intercourse (See Figure 4). The sheets 10 preferably have beveled cutting edges 11. The process takes place as follows: the material dispenser 1 is filled by the extruder screw 2 with a heated thermoplastic 3. The end 7 of the closure 6 moves then upwards in the direction of the wall of the material dispenser 1, disposed opposite the bottom 4 (see Figure 1), in such a way that the dispenser abort is released 5. A flow of thermo-material 12 comes out from the metering opening 5, shown by those made in Figure 1. Then, the metering opening 5 is closed by moving the closure body 6 downwards (see Figure 2). In this position, a flow part 'of material 13 is separated.

In this connection, the material flow part I 13 hangs on the lower end 7 of the closure body or due to the adhesion or adhesive properties of the thermoplastic material, which make it more difficult to separate the preform from the known processes ( see Figure 2). According to the exemplified embodiment, the closure body 6, with the material flow portion 13 hanging on its lower end 7, is subsequently further lowered, until the free lower end of the material flow portion 13 is supported by itself on the wall of the structure of the hollow mold 8 (see Figure 3). Subsequently, the cutting device 9 is actuated, and the sheets 10 are urged against each other, and separate the desired material portion 14 from the material flow part 13 (see Figure 4), whereby the portion of material 14 has a closed compact drop shape. Subsequently, the blades 10 of the cutting device 9 are driven back to their initial positions. The cutting device 9 can be configured with a vertical adjustability (not shown), in order to vary the size of the separate material portions 1. Also, it is possible to make a provision for a cleaning device (not shown), to clean the sheets 10 of the adherent plastic, if any, as it is? < cn leaves 10; This device can also be tensile, if needed. Preferably, the cutting device 9, and particularly its blades 10 are cooled (not shown) in order to largely prevent the plastic from adhering to the blades 10. For this purpose, the blades 10 can be provided with a alternative way or rl addition, with a coating against pegostiosity. The size of the material flow 12 exiting through the dosing opening 5 of the material doser 1 can be controlled by controlling the separation of the end 7 of the closure body 6, from the dosing opening 5, and / or the duration over which the dosing opening 5 is kept open. Also, it is possible to operate the cutting device 9 already in the position shown in Figure 2, where the material flow part 13 is still hanging freely over the lower end 7. of the closing body 6. If this possibility is selected, the portion of the separated material 14 would fall freely into the space of the hollow mold 8. It would thus be possible to calculate the frequency at which portions of material are produced, because the closing body 6 would have to periodically travel a recotri or shorter. By lowering the closure body 6 into the dispensing opening 5 (see Figure 2), the flow of material 12 practically stops, which enables a clean cut without further flow of the material. Stopping the flow of material can also be performed, for example, by briefly producing a vacuum inside the material dispenser, by means of the movement of a piston of a piston unit (not shown), in such a way that it can not exit more material through the open dosing opening 5 (see Figure 1).

Claims (7)

1. A process for producing an article molded from plastic, by separating individual material portions from a downwardly directed material stream of heat-plasticized plastic, exiting from a resealable metering aperture, from a metering device. material; transferring the portion of separated material into a hollow mold space; and compressing to a molded article closing the hollow mold space, characterized in that the separation of the desired material portion from the material flow below the dispensing opening, and separated from the latter, takes place by cutting sheets, whereby , the flow of material for the separation of a portion of material is briefly stopped.

2. The process according to claim 1, characterized in that the material flow is stopped by periodically closing the dosing opening.

The process according to claim 1 or 2, characterized in that a portion of the material flow is transferred by the closure body towards the hollow mold space, upon which, the desired material portion is cut from the portion of the material flow.

4. The process according to claim 1, characterized in that the flow of material is stopped by briefly producing a vacuum in the material doser.

5. A device for producing an article molded from plastic, with a hollow space that can be closed (8), and a dispenser of material (1) for heat-plasticized plastic (3), with a dosing opening ( 5) to dose a flow of plasticized material (12), this dosing opening is directed towards the hollow mold space (8), and can be closed by means of a closure body (6), and the material dispenser can be configured above the open hollow mold space (8), characterized in that a cutting device (9) is configured to separate desired portions of material (14), below and separate from the dosing opening (5), and because the closure body ( 6) is configured in such a way that it can be driven from a position that releases the dosing opening (5) from inside the material doser (1) to and through the dosing opening (5), and into the mold space hue open co (1), and can be retracted again.

6. A device for producing an article molded from plastic, with a hollow, lockable mold space (8), and a material dispenser (1) for heat-plasticized plastic (3), with a metering opening ( 5) to dose a flow of plasticized material (12), this dosing opening is directed towards the hollow mold space (8), and can be closed by means of a closure body (6), and the material dispenser can be configured above the open hollow mold space (8), characterized in that a cutting device (9) is configured to separate desired portions of material (14) below and separate from the dosing opening (5), and because the material dispenser is provided with a piston unit, with a movable piston to briefly produce a vacuum inside the material dispenser. The device according to claim 5 or 6, characterized in that the cutting device (9) is cooled.