DE102005015582A1 - Method and device for producing plastic moldings with internal cavity by means of injection of liquid, in particular water, and liquid injection device for this purpose - Google Patents

Abstract

The invention relates to a process for the production of plastic moldings having an internal cavity by means of injection of liquid, in particular water, an apparatus for producing such a plastic molding with internal cavity and a liquid injection device in the form of an injection nozzle. To create an internal cavity in the plastic mass injected into the cavity, liquid is introduced in a dynamic phase in accordance with closed-loop control under control of the liquid flow in accordance with speed, mass and / or volume. This is then followed by a static phase in accordance with a closed control of the liquid pressure to the final solidification of the plastic molding with internal cavity in the mold cavity for applying a compression pressure. In the apparatus for producing plastic moldings with internal cavity, a liquid injection device (25) is operated by means of a control device (26) that in a dynamic phase, a liquid flow in the form of a closed control in accordance with speed, mass and / or volume is introduced, and a switchover is made to a static phase in which, in accordance with a closed control, the fluid pressure is set and maintained until final solidification of the plastic molding (10) in the mold cavity (2) for application of a compression pressure. Furthermore, a ...

Description

The The invention relates to a method and a device for the production of plastic moldings with internal cavity as well with a liquid injection device therefor.

So far was it usual Manufacture plastic moldings with internal cavity by gas injection. Alternative was trying to plastic moldings with internal cavity by producing a liquid, in particular injects water instead of a gas. But there is one liquid Under the conditions of use for gas formation, there have been great difficulties so far with regard to the procedure, the interpretation of suitable devices and also with regard to the construction of suitable liquid injectors.

The Invention aims at overcoming the previously described Difficulty a method and an apparatus for manufacturing plastic moldings with internal cavity to provide which the production of plastic moldings with internal cavity through Use of a liquid instead of gas, especially water. Also, a liquid injection device is intended be prepared, which in the production by means of liquid injection easy to use.

To The invention is for this purpose a process for the production of plastic moldings with internal cavity by injection of liquid, in particular water, provided in a plastic mass injected into a mold cavity, which is characterized in that for generating the inner cavity in the injected into the mold cavity plastic mass, the liquid in a dynamic phase according to a closed control under control of the liquid flow in accordance with Speed, mass and / or volume is entered, and then in a subsequent static phase according to a closed control of fluid pressure until the final solidification the plastic molding with internal cavity in the mold cavity for application a compaction pressure is maintained accordingly.

At the inventive method Thus, a dynamic influence of the liquid flow takes place for forming the inner cavity in a plastic mass, which into a mold cavity of a mold has previously been injected. Dependent on from the properties of the plastic compound and / or in the plastic molding To be generated inner cavity can thus in the method according to the invention the liquid flow considering of speed, mass and / or volume in the form of a closed Control be controlled. This allows a sensitive vote on the materials to be processed but also under consideration whose configurations are made. They are also here used fluids, like water, inexpensive to disposal. For applying a compaction pressure on the plastic molding with internal cavity is according to the invention in a static phase also according to a closed control the fluid pressure upright received, so that one the wished Compaction pressure can be maintained, which is required to the to be produced plastic molding with internal cavity the final shape design possible to give true to form.

Preferably will that during the dynamic phase injected fluid volume, the fluid pressure and other factors such as the time, supervised. This can be a precise vote and setting the generation of the interior cavity during obtained the dynamic phase.

Preferably are the pressure parameters for the liquid pressure in the static phase user-selectable. As a result, in particular, depending on the used Plastic material ensures that until solidification sufficient Compression pressure is maintained, and qualitatively make high-quality plastic moldings with internal cavity.

Conveniently, takes place in the process management according to the invention, the switch from the dynamic to the static Phase as required of one and / or several different influencing variables. in this connection it may be an injected fluid volume, a fluid pressure magnitude, a Size of the print in the mold cavity, the passage of the plastic mass on a sensor in the Mold cavity and / or time acting. In each case suitable parameters can be selected by the user without difficulty.

According to one preferred embodiment of the method according to the invention is during the dynamic phase of the interior cavity in the creation of Plastic molding resulting excess of the plastic mass to the material feed side returned or in a secondary cavity passed, so that the Sprue with the produced plastic molded part is ejected.

To negative effects of plastic To avoid residues or venting air in the area of the liquid-carrying lines in the next production cycle, in the method according to the invention, preferably after each injection cycle, a rinsing process is carried out in which the liquid-carrying lines are freed from harmful substances. In this way, one can continuously ensure a consistent quality in the products produced according to the invention.

Further is according to the invention, a device for the production of plastic moldings provided with internal cavity. Such a device has one Mold cavity, an injection device for injection of the plastic mass into the mold cavity, a liquid injection device and a control device for the liquid injection device. In the production apparatus according to the invention directs the control device for the liquid injection device in a dynamic phase, the liquid flow in the form of a closed scheme as specified of speed, mass and / or volume. In this dynamic Phase is the internal cavity in the injected plastic mass generated in the mold cavity.

Further the controller takes a switch to a static Phase before, in accordance with a closed-loop control of fluid pressure is set and maintained to provide sufficient compaction pressure, until the plastic molding is finally solidified in the mold cavity and from the Mold cavity can be removed. Thus one has only one Control device, here in closed control the liquid flow in the dynamic phase controls and switching to the static Phase performs. This simplifies the control effort in the manufacturing apparatus of the invention. Also takes over the control device influencing in the form of a closed Regulation of fluid pressure until the final Solidification of the plastic molding.

According to one preferred embodiment of Manufacturing device monitored the control device in the dynamic phase, preferably by means of Sensors, the injected liquid volume, the fluid pressure and / or other sizes by means external signal generator. Thus, you can during execution the dynamic phase different influencing factors considered in the manufacture of plastic moldings with internal cavity become.

Preferably if the control device in the production device according to the invention is electrical, electronic, hydraulic, pneumatic or in the form of combinations thereof operable. Thus, there is a variety of drive options for the Control device available.

Also becomes according to the invention, a liquid injection device for one Device for producing plastic moldings with internal cavity provided, which is characterized in that Shape of an injection nozzle is designed, and the nozzle tip protrudes into the plastic mass, which previously in a mold cavity has been injected. Preferably, the injection nozzle protrudes in Entformungsrichtung into the interior of the plastic mass. Conveniently, it is designed as a slide valve, which opens only when applying a pressurized liquid and a liquid flow approximately perpendicular to the Entformungsrichtung emits. Thus, the injector is always reliable across from the mold cavity and the inner cavity to be generated in the plastic molding sealed. Because the liquid flow is discharged approximately perpendicular to Entformungsrichtung can be Difficulties in demolding of the produced plastic molding avoid with internal cavity. Also, this can be post-processing avoid.

The injection the liquid injection device according to the invention is preferably designed such that it is electrically, electronically, hydraulically, pneumatically or in combination can be operated from this. Thus one can each desired and suitable control for the injector provide.

In summary it is essential in the invention that the inner cavity in the injected plastic mass is generated dynamically and this closed-loop control according to speed, Mass and / or volume of the liquid in preferred settings of the corresponding fluid flow carried out becomes. After generation of the inner cavity in the plastic molding is then in a static phase according to a closed control the fluid pressure up to the final Solidification of the plastic molding maintained. With the help of injected liquid read accurately form plastic moldings with high quality, the liquids used a kostengün stigen Ensure production process. Also, such a method of preparation by means of liquid, like water, more environmentally friendly.

The The invention will be described below with reference to preferred embodiments with reference to the attached Drawing closer explained. The following applies:

1 - 3 schematically show the procedure for producing a plastic molding with internal cavity, taking into account the corresponding production phases;

4 shows in a schematic view an alternative manufacturing variant for a plastic molding with internal cavity, in which the resulting in the generation of the inner cavity excess of the plastic material is returned to the material feed side;

5 shows schematically an apparatus for producing plastic moldings with internal cavity according to the invention, by means of which the inventive method for producing plastic moldings with internal cavity can be carried out and realized; and

6 a schematic sectional view of a liquid injection device in the form of an injection nozzle.

Based on 1 to 3 schematically an embodiment of the process flow for producing a plastic molded part with inner cavity is explained. Also, there is shown in principle the basic structure of a device for producing such a plastic molded part. Out 1 is a total with 1 designated form to see in which ge closed form 1 a mold cavity 2 is formed. In this of the form 1 formed mold cavity 2 is according to the representation of 1 a plastic mass 3 For example, a polymer injected. The injection is in 1 indicated by an arrow. After injecting the plastic compound 3 becomes the cavity 2 completely filled, and the plastic mass is schematically in 1 With 3 entered.

Out 2 It can be seen that in the injected plastic material 3 gradually an internal cavity 4 is formed, which is achieved for example with the aid of a liquid injection device not shown there. In this in 2 the production phase of the liquid injection device is controlled dynamically by means of a control device, wherein a liquid flow in the form of a closed control in accordance with speed, mass and / or volume is introduced. Like also out 2 is seen in the generation of the internal cavity 4 a portion of the previously injected plastic mass 3 in this example, in the direction of the sprue or a so-called secondary cavity from the mold cavity 2 the form 1 displaced, with the aid of a schematically illustrated piston-cylinder arrangement, a predetermined pressure control for the generation of the inner cavity 4 is set and made. The in the production of the inner cavity 4 resulting, displaced, excess plastic mass is in the 2 and 3 With 5 designated. This can be a regulation for the excess plastic mass 5 be realized in the form of a closed loop. Schematically, control devices are in the figures 7 and 8th indicated, which can operate electrically, hydraulically, pneumatically and also in the form of combinations thereof, to influence the corresponding flow rates and pressures in a controlled manner. The schematic with 8th indicated control device illustrates a control system with closed or open loop.

In the schematic representation after 3 is the internal cavity by means of the liquid injection device 4 in the plastic mass 3 completely generated and the control system is procedurally in a static phase, in which in accordance with a closed-loop control of the liquid pressure to the final solidification of the plastic molding 10 in the mold cavity 2 is set and maintained to apply a compression pressure. After solidification can then in 3 schematically to be seen plastic molding 10 with the inner cavity shown there 4 out of form 1 be removed and during the manufacturing process of the plastic molding 10 resulting, displaced, excess plastic mass 5 is after removal of the plastic molding 10 out of form 1 removed as a gate.

In 4 schematically illustrates an embodiment of a manufacturing method for a plastic molding with an inner cavity. The same or similar parts are provided there with the same reference numerals. As an essential difference to the above with reference to the 1 to 3 explained embodiment is in the process guide after 4 during the creation of the internal cavity 4 By means of liquid injection displaced, excess plastic mass 5 pushed back in the direction of the injection side.

In this procedure, a plastic molding 10 with an internal cavity 4 also produced with the realization of a dynamic and a static phase. Switching between these phases is dependent on the values of monitored parameters. In the dynamic phase, the formation of the internal cavity 4 in closed loop depending on the different cross sections available. During this dynamic phase can be used as a parameter the volume of the injected liquid or the volume of the displaced plastic mass 5 or the pressure of the liquid in the plastic molding 10 or the pressure in the mold cavity 2 or possibly the passage of the displaced plastic mass at one in the mold cavity 2 arranged sensors (not shown) or the time to be monitored. At the option of the user, the switching may be initiated in the static phase depending on one or more of the aforementioned parameters. In the subsequent static phase is by means of a pressure control of the inner cavity 4 in plastic molding 10 maintained.

In the dynamic control of the process according to the invention, the flow rate of the liquid introduced or in the case of the example according to the 1 to 3 the increase in the volume of the displaced, excess plastic mass 5 Consideration. This gives the advantage that the inner cavity 4 depending on the properties of the material (plastic) or the geometry of the internal cavity to be generated 4 can be realized.

5 shows schematically an apparatus for the production of plastic moldings with internal cavity, and this figure also serves to schematically illustrate the process sequence according to the invention. Here are the form 1 and the mold cavity 2 indicated only schematically and the Entformungsrichtung is indicated schematically by arrows. Also is with 20 a total of an injection device for a liquid for generating the inner cavity 4 shown. As an example of a liquid, water is assumed here in a preferred embodiment. The injector 20 , which is also referred to as a liquid injection device, is in the form of an injection nozzle 21 designed, whose nozzle tip into the mold cavity 2 injected plastic compound 3 protrudes in Entformungsrichtung. The injector 21 is preferably designed in the form of a slide valve which emits a liquid flow preferably perpendicular to the Entformungsrichtung only when applying a pressurized liquid, as in 5 schematically with an arrow 22 is indicated. This injector 20 ensures a seal with respect to the plastic mass and the nozzle tip is in the form of the 1 Mold cavity formed in the closed state 2 , By this design, a demolding of the plastic molding with internal cavity in Entformungsrichtung (in 5 indicated by arrows) allows without an undercut in the plane of the injector 20 is available. As a result, can be plastic mass residues at the level of the injector 20 avoid and in particular there is an introduction of the liquid flow 22 approximately at right angles to the Entformungsrichtung.

The injector 20 includes a chamber 23 and a chamber 24 , The injector 20 injects liquid in the direction of the arrow 22 characterized in that the liquid in the chamber 23 is pressurized. Via a circuit B, a displacement of the piston of the injector takes place 20 and the injector 20 directs the liquid according to the arrow 22 into the plastic mass in the mold cavity 2 one. Furthermore, the injector includes 20 a check valve 25 which is only one passage from the chamber at a certain operating pressure 24 to the chamber 23 allowed. The injector 20 has a decentralized tightness for the liquid to be introduced, so that a leakage of the liquid toward the cavity and / or the plastic mass effective in applying a pressure to the liquid in the chamber 23 is avoided. About the in 5 schematically indicated circuit A is a pressure to the liquid in the sealed chamber 24 via a schematically indicated control and regulation system 26 a sufficient resultant force is maintained to provide a seal with respect to the molten plastic mass at the level of the injector 20 and to maintain their exit side. In this phase, the chamber remains 24 Reliable tight, if that of the control system 26 applied pressure does not exceed the pressure, which could cause the check valve 25 opens.

When the liquid escapes into the plastic compound 3 via the circuit B, a filling of the circuit B is effected with a liquid and / or gas. After this phase will be through the control system 26 an overpressure to the liquid in the chamber 24 applied so that the check valve 25 opens. Thus, the entire circuit B can be filled with liquid while in the region of the chamber 23 a tight seal is present.

Like also in 5 is indicated schematically, can also realize a cycle A ', which is a rinsing phase, which is carried out, for example, after each production of a plastic molding with internal cavity to rid the fluid circuit of plastic residues or gas. As schematically in broken line in 5 is registered, there is a fluid circulation by means of the control and regulating system 26 over the open check valve 25 so that the liquid from the chambers 24 and 23 can be circulated in a kind of short circuit. As a result, plastic residues or other interfering substances can be removed from the liquid circuit.

In 6 schematically is an embodiment of an injection device 20 shown closer. This injection device 20 for the liquid is as an injection nozzle 21 designed. Also there are the chambers 23 and 24 shown and are schematic the connections for the circuits B and A indicated. Thus, the circuit B flows into the chamber 23 and the circuit A is in communication with the chamber 24 , Also, the corresponding seals in the injector 21 indicated. With the help of a circuit B, a pressure on the liquid in the chamber 23 about the control system 26 to 5 created. The slide valve of the injector 20 shifts, and it may be at the head end of the injector 21 as in 5 indicated in the direction of the arrow 22 Liquid are discharged. This in 5 shown check valve 25 is closed, so that the liquid from the chamber 24 regardless of the chamber 23 can drain.

After making a plastic molding with internal cavity in the mold are in the chamber 23 Liquid but also plastic residues and ventilation air included. In the next production cycle for a plastic molding with internal cavity this would be harmful. Therefore, to initiate a rinse cycle, an overpressure to the liquid in the chamber 24 about the control system 26 applied so that the check valve 25 opens. Thus, a purge cycle according to the circuit A 'can be run while the injector 21 by a corresponding tight closure of the chamber 23 is closed and remains closed.

In the method according to the invention and the apparatus for this purpose is determined in a plastic material 3 which are in a mold cavity 2 a form 1 injected, an internal cavity 4 formed by influencing the evacuation speed in a closed loop as a function of the existing cross sections and taking into account the resulting pressure during monitoring. After the formation of the cavity or inner cavity 4 there is a switch to a pressure control in a static phase. In this method, in particular, the cavity or the inner cavity 4 by injecting a liquid with a suitable injector 20 formed in a controlled manner. The transition from the dynamic phase with liquid injection, in particular water injection, to the pressure control in a static phase until solidification of the plastic molded part to be produced 10 with internal cavity 4 may take into account the displaced plastic volume, the volume of fluid injected, the fluid pressure magnitude, the magnitude of the pressure in the internal cavity 4 , the passing of the plastic mass on a sensor in the mold cavity 2 or as a function of time. In the static phase, the plastic mass is held until the end of solidification under a compaction pressure, which is due to the pressure of the liquid, the pressure of the piston of a dynamic sprue (plastic mass displacement) or a movable part in the cavity 4 is produced, controlled. In the static phase is preferably a control of the liquid flow rate at about 0, which is maintained in order to achieve an isochoric keeping constant of the pressure.

Although above preferred embodiments explained according to the invention Of course, the invention is not limited to this, but there are numerous modifications and Modifications possible, the expert will meet if necessary, without the spirit of the invention to leave.

1

shape all in all

2

mold cavity

3

Plastic compound

4

internal cavity

5

Displaced, excess plastic mass

7

control device

8th

control device

10

Plastics molding all in all

20

Injector all in all

21

injection

22

arrow for issued liquid

23

chamber

24

chamber

25

check valve

26

Tax- and control system

Claims (11)

by injecting liquid, in particular water, into a plastic mass injected into a mold cavity, characterized in that, to produce the internal cavity in the plastic mass injected into the mold cavity, the liquid in a dynamic phase according to a closed-loop control under the control of the process for producing plastic moldings Internal cavity fluid flow is registered in accordance with speed, mass and / or volume and that is then maintained in a subsequent static phase according to a closed control of the liquid pressure until final solidification of the plastic molding with internal cavity in the mold cavity for applying the compression pressure. Method according to claim 1, characterized in that that in the dynamic phase the injected liquid volume, the liquid pressure and the time is monitored by means of an external signal generator. Method according to claim 1 or 2, characterized in that in the static phase Pressure parameters for the fluid pressure can be selected by the user. Method according to one of the preceding claims, thereby in that the Switching from the dynamic to the static phase in accordance with at least one of the following influencing variables occurs: - displaced plastic mass, - injected Liquid volume, - fluid pressure, - size of the print in the mold cavity, - Passing the plastic mass on a sensor in the Mold cavity and / or - Time. Method according to one of the preceding claims, characterized characterized in that during the dynamic Phase for generating the inner cavity in the plastic molding of the excess of the plastic mass returned to the material task side or in a secondary cavity directed and ejected with the produced plastic molded part. Method according to one of the preceding claims, characterized characterized in that the production of a plastic molding with internal cavity the fluid handling Cables for the removal of plastic residues and ventilation air flushed become. Device for producing plastic moldings ( 10 ) with internal cavity ( 4 ) with a mold cavity ( 2 ), an injection device for injection of the plastic material ( 3 ) in the mold cavity ( 2 ), a liquid injection device ( 20 ) and a control device ( 26 ) for the liquid injection device ( 20 ), characterized in that the control device ( 26 ) the liquid injection device ( 20 ) in a dynamic phase, the fluid flow in the form of a closed control in accordance with speed, mass and / or volume and initiates a switch to a static phase in which in accordance with a closed-loop control of the liquid pressure to the final solidification of the plastic molded part ( 10 ) in the mold cavity ( 2 ) is set and maintained to apply a compression pressure. Apparatus according to claim 7, characterized in that the control device ( 26 ) in the dynamic phase, preferably by means of sensors, the injected liquid volume, the liquid pressure or other variables monitored by external signal generator. Apparatus according to claim 7 or 8, characterized in that the control device ( 26 ) operates electrically, electronically, hydraulically, pneumatically or in the form of combinations thereof. Liquid injection device for an apparatus for producing plastic moldings with an internal cavity, characterized in that it is in the form of an injection nozzle ( 21 ) is formed, whose nozzle tip into a mold cavity ( 2 ) injected plastic compound ( 3 ) preferably protrudes in Entformungsrichtung and is designed as a slide valve which opens only when applying a pressurized liquid and a liquid flow ( 22 ) preferably perpendicular to the Entformungsrichtung emits. Liquid injection device according to claim 10, characterized in that the injection nozzle ( 21 ) is electrically, electronically, hydraulically, pneumatically or in the form of a combination thereof operable.