DE4331207A1 - Process and apparatus for plasticising and injection-moulding - Google Patents

Abstract

Process for injection-moulding moulded parts in cycles by means of an apparatus for producing injection-moulded parts, in moulding compound, comprising a preplasticising cylinder with a conveying screw for plasticising the moulding compound, an injection device with injection cylinder and an injection plunger for transferring the plasticised moulding compound into a mould, in which the moulding compound is then polymerised or crosslinked, the plasticising of the moulding compound for the injection operation of the next following cycle, involving transfer into a first receiving volume, commencing already while the injection operation of the moulding compound of the preceding cycle out of the second receiving volume into the mould is still going on, and either the two receiving volumes being alternately filled during plasticising and emptied into the mould in successive cycles or a transfer of the moulding compound from the first receiving volume into the second volume taking place during the cycle within a period of time which is short in comparison with the duration of the overall cycle.

Description

The invention relates to a method in the preamble of claim 1 specified type and a device for Execution of the procedure.

Injection molding processes are different for the production Next molded parts made of plastic molding compounds.  

In injection molding machines are different versions of Injection units known, of which the machines with one combined screw and piston injection unit for Plasticizing mostly benefits compared to the earlier usual arrangements with either screw or piston offer injection unit. So come as molding compounds probably plastics as well as elastomers and thermosets in Be dress.

Plasticization takes place in known injection molding processes raw material for the subsequent work cycle because after the injection process of the previous work tactical instead. When designing the injection molding machine is made by choosing an appropriately powerful Plasticizing unit tries the plasticizing process within those necessary to cross-link the molded parts End heating time. With higher clock speeds and shorter crosslinking or polymerization times the requirements for the plasticizing unit are increasing and lead to technically complex units in which the increase in the design effort to do so time advantage predominates.

An injection unit is known from DE-30 14 072 A1, which in particular for moldings with a foamed core and compact outer skin can be used. Here it is in the Screw plasticized material first in the Storage cylinder pressed and after switching a U- shaped connecting channel from the storage cylinder under transferred to the injection mold at high pressure. Here is the water connecting channel designed so that each time  the next spraying process, initially fresh unfoamed Ma material from the front area of the storage cylinder in the injection mold arrives and only at the end of the stroke of the com primed foam that is immediately before the injection molding piston is located. This prevents foamed Material already in the start of the spraying process Injection mold and thus also on the surface of the molded part arrives, so that there are pore-free and streak-free surfaces of the molded part.

Furthermore, in DE-35 36 592 B1 there is an injection unit described by a particularly compact design, the advantage fortunately has very short flow paths. Thereby it is avoided that the raw material to be processed due to long dwell times in heated injection areas changed in quality or by Ab cooling solidified if not additional precautions to be hit. This arrangement is only for the Production of small precision parts can be used.

Furthermore, in DE-35 01 846 A1 a device for re described the spraying process in which the molten zene plastic into the injection mold under a precise ge regulated pressure is filled. This will be a very high Filling speed chosen to slow growth to achieve the spray skin, so that among other things can achieve a higher dimensional stability. Then The external pressure is removed very quickly to the Compression of the molding compound by relaxing the im To compensate the molded part accumulated pressure. The con Constant holding pressure is applied until the potting  of the sprue is finished, while the internal pressure in the Injection mold escapes.

From DD-2 46 078 is also a method for rain development of the spraying process, in which a switchover from a high filling speed to a lower one Conveying speed for pressing and takes place Pressure occurring during the filling process is measured and added together with the filling time as a comparison parameter for the rain tion of the spraying process is used.

DD-2 62 620 also describes a method for reducing Reduction of the cycle time in the production of molded parts known from thermosets and elastomers. This method is particularly suitable for injection molding thick-walled molds parts applicable by considering the further reaction during the crosslinking of the polymeric molding composition after the De-molding of the molded part.

Finally there is a device in EP-0 287 001 A1 described for injection molding by a conical Design of the injection piston head of the injection cylinder the closure of the spray head allows so that slightly liquid molding compounds without the usual tend problems with the most commonly used locking mechanism nisms (e.g. residues of molding compound) can be processed.

All constructions mentioned so far have the disadvantage on that a significant reduction in the cycle time at the intermittent production of injection molded parts is not possible  is. This is disadvantageous in that the host These processes are particularly economical from the Pro Productivity of the injection process and, above all, of the time it takes to make an injection molded part or an injection molding set in the manufacture of Multiple benefit is needed depends.

The invention is based, with a Ver drive the genus mentioned the clock speed speed without increasing the performance of the Plasti finishing device. In addition, a pre direction specified for carrying out the method.

This task is min the characteristic features of the Claim 1 solved.

The invention includes the knowledge that it is for op timely utilization of the plasticizing tool is favorable, if this is already one during the spraying process Volume supply of plasticized molding compound produced and for the next spraying process of the next work cycle keeps in stock.

Depending on the type of filling and emptying of a pre advice volume can be the last-in-first-out (LIFO) or the first-in-first-out (FIFO) principle for the use of com men. In the former case, it can - if there is a corresponding Dimensioning the dwell times - that the Time taken by a plasticized volume element until Reaching the final position in the form is needed is essentially constant, so that any  Networking or aging processes that are already on the Step into the form, equally advanced are. With the FIFO principle, this condition is fulfilled and there are advantages if the time for the injection process itself is kept quite short, so that here with no significant delays to be compensated surrender. LIFO and FIFO principles differ in he line through the filling of the injection cylinder, which with LTFO from the exit side with syringes, with FIFO however, from the piston side.

The advantage of the solution according to the invention comes in particular re valid if the time required for the Feeding raw material from the screw into the inlet injection unit and the plasticizing time to a significant extent are determining the cycle time and also the injection time in the injection mold has the same order of magnitude as that subsequent heating time for networking or the if necessary, subsequent cooling phase in the spray shape.

A major advantage of the present invention be is therefore in that the injection and plasticizing be significantly shortened together during injection molding.

The invention includes a method for time decoupling pelt plasticizing and injection during injection molding of polymeric molding compounds and a device for through management of the process, whereby by plasticizing maximum plasticizing time even during injection also for almost the entire duration of the networking is available.  

Both plastics and elasto come as molding compounds mers and thermosets.

In an advantageous development of the invention essen process can also by optimal preheating the mass injected into the mold cavity that is necessary in the mold cavity heating time can be significantly reduced.

At the same time there is the possibility of the injection time to largely adapt to the requirements of the material sen and extend, because on the one hand it helps to achieve economic cycle times no temperature increase through Dissipation must be done in narrow sections and others on the one hand the risk of cross-linking of the molding compound at long flow in the hot mold cavity through targeted heating is switched off depending on the remaining flow path. Here is it is particularly important that during the shortened networking times, overall reduced cycle not only the time available for plasticizing standing period is increased, but also the one injection molding process with regard to the throughput of molding compound can be varied without an extension of the one spraying time to a substantial extension of the whole Cycle time leads, during the injection in each If the plasticizing process can be continued.

In contrast, with the conventional injection molding process plasticizing the mold only after the injection process mass instead. When designing the injection molding machine is made by choosing an appropriately powerful Plasticizing unit ensured that the plastifi  ornamental process within the need to crosslink the molded parts agile heating time can be ended. Accordingly, the Process parameters selected in production. In general the plasticizing process is clearly before the heating expires time ended.

With so-called shaving head injection molding, however, it is necessary maneuverable to change these design criteria because not sufficient heating time for the largely free choice of Plasticizing parameters are available. Among these before The plasticizing time is suspended together with the prior injection phase at a cycle time determined and thus the economy of the injection molding pro influencing process. Factor. So it turns out to be favorable, the phase of injection while preheating the Extend molding compound at the expense of crosslinking time, whereby by the parallel injection plastifi decorate enough time for the latter process Is available and overall even with a time saving can be expected.

In a further preferred embodiment of the invention dung can be dosing accuracy when injecting the injection mold even with large plasticized volumes increase what is achieved by having different Injection cylinder sizes are used. By that dosing volume and the corresponding fine adjustment of the dosing volume is a better pressure consistency at the Zy mild exit possible.

Another advantage of the method according to the invention is the complete waiver of any setbacks  tile in the injection unit also during processing right relatively light-weight molding compounds, with their injection molding conventional injection molding machines not without closures mechanisms can be worked. This will avoid that dead water areas arise, which experience has shown Can cause problems in operation.

In addition, as mentioned before, there is one whose embodiment has the advantage that the first of the Feed screw exiting raw material also first the injection mold is injected (FIFO: First in first out). In this case, the average dwell time of all volumes elements of the molding compound in the injection unit, see above that an efficient optimization of the heating power to the Pla stification can take place. This prevents a individual areas are not yet fully plasticized and other parts of the molding compound by overheating or too long thermal stress, for example due to thermi reduction in which quality is restricted.

To realize the advantages mentioned serve the directions for performing the inventive method rens according to the distinctive parts of the corresponding Device claims with which it is possible already during the entire injection phase into the injection mold and the subsequent crosslinking and cooling phase Raw material for the next injection process to plastifi adorn.

In a first embodiment, at least two are one injection cylinder provided with the feeder  worm cylinder on one side and with the one Spray channel to the injection mold on the other side Multi-way valve are connected, so that for example in Case of two injection cylinders either of the screws cylinder with the first injection cylinder and the second Injection cylinder with the injection channel or the Screw cylinder with the second injection cylinder and the first injection cylinder is connected to the injection channel they are.

In an advantageous variant in this Ausfü form two different sized injection cylinders used. The larger one is used for plasticizing and on injection of the larger proportion of the molding compound into the Injection mold and the smaller one for the remaining filling of the spray form and for pressing to create a high pressure in the injection mold to compensate for the shrinkage to reach the molding compound on cooling.

In the first device variant, the arrangement mentioned is used in a first work cycle the first Injection cylinder with raw material from the screw cylinder the fill and then the raw inside plasticize material. At the same time, the second injection cylinder the already plasticized mate rial into the injection mold via the injection channel splashes. For the second cycle, the valve is turned switched. In this phase, the emptied second one injection cylinder over the feed screw again with new em polymeric raw material, which is then in the injection cylinder is plasticized by heating,  while at the same time the plasticized molding compound from the first injection cylinder into the Injection mold is injected.

In a second device variant, which is preferred Injection cylinders of different sizes, the Injection process for a molded part in two injection phases divided, in the first phase the plasticized form mass from the larger of the two injection cylinders into the Injection mold is injected. Meanwhile, the with smaller injection cylinders via the feed screw filled with new polymer raw material, which then plasticized by heating in this injection cylinder becomes.

With almost complete filling of the injection mold, this will be Valve quickly switched and immediately after that remaining amount of plasticized molding compound from the smaller injection cylinder via the injection channel into the Injection mold emptied. By applying high pressure molding compound is pressed into the injection mold. During that The larger injection cylinder is fed through the feed auger filled with new polymer raw material, the is then plasticized by heating. These The second phase serves, among other things, the one for the night press, that means the one for the complete filling of the Injection mold required pressure to build up.

In the second embodiment, the entire injection unit in a very compact design. For this purpose, the feed screw is in a storage cylinder  the arranged that at the same time as a plasticizing cylinder serves. This cylinder is in turn in a second one injection cylinder axially movable. Between the two A check valve is attached to cylinders. The one In this case there is a spray channel to the injection mold the bottom surface of the second cylinder.

In a special variant of this embodiment the injection channel to the injection mold is not on the bottom surface of the injection cylinder attached, but is in its Wall recessed as a groove in a hole in its side wall opens.

In all variants, the injection process can be preferred monitored by a pressure or mass flow control and can be controlled to constant and reproducible spray to achieve conditions.

Other advantageous developments of the invention are in the subclaims or are identified below along with the description of the preferred embodiment the invention with reference to the figures. It demonstrate:

Fig. 1 is a schematic side view of a first embodiment of an injection unit for imple out the method according to the invention,

Fig. 2 is an illustration of a detail of the device according to Fig. 1,

FIGS. 3a and b are schematic side view of another apparatus for carrying out the procedural proceedings invention in two different working positions, as well as

FIGS. 4 and 5 are schematic side views of variants of the device of FIG. 3.

In the basic representations of the Designs according to the invention are only the radio tion elements shown schematically. It is clear Lich that the mechanical control by suitable Ak tivators according to the conditions mentioned by suitable processor-based control devices can take place.

In the schematic side view of an injection unit with a screw unit shown in FIG. 1, two essentially identical plasticizing and one injection cylinder with a two-way valve are provided. This embodiment of the device according to the invention works according to the LIFO (last in first out) principle.

Essential in this embodiment is the use of at least two injection cylinders 2 and 4 with an injection plunger 1 and 3 , the cylinder with the feed screw 5 , in which the feed screw 6 is guided, on one side and with the spray channel 8 with one of these passes Heating device 9 with a rotating shaving head 9 a. In continuation of the spray channel, the injection mold 10, not shown, adjoins the shaving head. The assemblies are connected via a two-way valve 7 shown in FIG. 2 in such a way that either the screw cylinder with the injection cylinder 1 and the injection cylinder 3 are connected to the injection channel or the screw cylinder with the injection cylinder 3 and the Injection cylinder 1 with the injection channel.

To make these connections, the valve shown in Fig. 2 is used in detail, it being apparent that by rotating the hatched, around the selected axis of rotation cylindrical body by 180 ° un different pairs each a corner of adjacent inflow or outflow openings with each other are connectable.

For the operation of this arrangement, crosslinkable Formmas se is first transferred through the feed screw from the screw cylinder through the valve into the injection cylinder 1 and plasticized there. During this phase, previously plasticized molding compound is injected from the injection cylinder 3 via the valve and the injection channel into the injection mold.

After completion of the injection process and the crosslinking of the molding compound in the injection mold, the molded part is removed from the injection mold and the valve is brought into the other position for the start of a new supply process. Subsequently, polymeric raw material from the screw cylinder through the valve into the injection cylinder 3 leads and plasticized there. Meanwhile, the injected be already temporarily in the injection cylinder 1 existing plasticized molding material through the valve and an injection channel in the injection mold. Suitable pressure profiles can be run.

In another embodiment, not shown in the drawing, differently sized injection cylinders of FIGS. 1 and 3 are used. In this case, the entire injection process is divided into two different pressure phases. In the first phase, the raw material that has not yet been plastified is first led out of the screw cylinder via the valve into the larger injection cylinder 1 . At the same time, the injection process for the molded part to be produced in the previous injection phase is carried out by injecting the remaining amount of plasticized molding material from the smaller injection cylinder 3 , through the injection channel, into the injection mold. For this purpose, a lower pressure for the complete filling and com pensation of the shrinkage occurring when the molded part cools down is exerted on the molding material, which is referred to as so-called "repressing". The different pressure phases with successively actuated pistons of different sizes will enable a more precise materia long-matched pressure and quantity metering.

Then the molded part is removed from the mold and the valve briefly switched to its other passage position and then in the second phase the plasticized molding compound for the next molded part is injected from the larger injection cylinder 1 via the valve and the injection channel into the injection mold. Meanwhile, the smaller injection cylinder 3 from the Schneckenzy cylinder through the valve is filled with polymer raw material, where the raw material is then plastifi ed by heating.

Let with the embodiments described above particularly short cycle times and thus a high pro ductility of the injection molding process because the po polymeric raw material is continuously plasticized. Be already during the previous injection phase Injection mold from one injection cylinder can be new raw material via the feed screw in the other one injection cylinders are injected so that the spraying process for the production of the next molded parts even at extreme short heating and cooling times immediately after the Demoulding of the previous injection cycle can be made molded parts and no additional loading working time required for the plasticizing process is.

In a further, not shown in the drawing, a variant of the guide are in one position of the valve 7, the plasticizing unit 5 and the piston 1 on the one hand and the cylinder 3 and the injection path (via the preheating unit 9 ) on the other hand. While the plasticized molding compound is transferred into the interior of the cylinder 1, which forms the first volume, in the manner of an intermediate store, the cylinder 4, with its piston guided therein, serves as an injection unit, so that injection and plasticization take place at the same time. In a further sub-work cycle, the cylinders 1 and 3 are then connected to each other by switching the valve 7 in its second position, blocking off the other paths, so that transferring the stored plasticized between two spraying operations during the heating-up time with only a short-term interruption of the plasticizing process Molding compound can be made from the "storage cylinder" into the "injection cylinder" 3 .

In the in Figs. 3 and 3a are schematic sectional views represented another embodiment of an injection unit with an opening provided in the storage cylinder cylinder for the intermediate storage of the plasticized during the injection process material, the interior of the piston itself forms the injection cylinder. The outlet opening to the injection mold is provided in the bottom surface of the injection cylinder and connects again to the valve unit 7 . (This embodiment of the device according to the invention works according to the FIFO [first in first out] principle.) The plasticized molding compound is injected during the phase shown in FIG. 3 through a connection path (arrow A) produced by means of valve 7 between the piston 3 'and the pre-connected heater 9 . In the meantime, the plasticizing screw 10 continues to work and fills a cavity located on its end face, while the screw 10 moves away in the opposite direction (arrow B) due to the molding compound to be added in the direction of arrow C.

Finally, the valve 7 in such a position is set after termination of the spraying process that the accumulated plasticized molding material is ejected by moving the screw 10 in the direction of arrow C 'in the injection piston 3' in the cavity 11 a in the cylinder 11, the piston 4 'Moves back accordingly. This means that this solution can be plasticized practically continuously, regardless of the injection process. Here, the LIFO principle is used again.

In FIG. 4, a further embodiment of the device OF INVENTION to the invention is shown. In this case, the injection cylinder and the plasticizing unit are combined in a compact unit, which also works according to the FIFO principle, so that the volume elements of the plasticized molding material have the same average residence time in the plasticizing and injection unit. The feed screw 10 is stored in a storage cylinder 11 ge and feeds raw material into the cavity 19 in front of the screw. Here, the storage cylinder, which is the same if designed as a piston in the injection cylinder 13 , moved such that it between the check valve 12 closed by a return surface 15 of the SpeI cherzylinders and the screw head leaves a cavity 19 out, which during this process with the fills not yet plasticized raw material and is already plasticized during this filling by an appropriate heating. At the same time, the molding compound already in the injection cylinder and previously plastified by heating is expressed through the lower outlet opening 14 and thereby reaches the injection mold arranged behind it.

In the next step, the molding compound located in the storage cylinder is transferred by moving the storage cylinder in the injection cylinder through the check valve into the cavity 20 in the injection cylinder. A backflow of molding compound over the screw flights is prevented, if necessary, by a suitable non-return valve, not shown.

A modified embodiment of this basic construction, which is shown schematically in FIG. 5, allows operation according to the LIFO principle. In this case, the outlet opening of the injection cylinder is not attached to its bottom surface as described above, but is designed as an axial groove 17 in the side wall of the injection cylinder, which leads to the bottom surface 16 opposite the end of the injection cylinder and has a length that is greater than the maximum stroke length of the storage cylinder, so that it ends above the bottom surface 15 when the storage cylinder is in the upper position. At this point, the groove merges into a bore 18 in the side wall of the injection cylinder, which has a connection to the injection mold, not shown.

Also with the embodiments described above in compact design can be a significant reduction the required cycle time of the injection process are sufficient because in contrast to the conventional methods pre-continuous plasticization of the molding compound is taken. While in the previously known methods During the injection phase into the mold, a plastic decoration in the injection cylinder can not be made can because the injection cylinder during this phase plasticized molding compound injected into the injection mold, can with the embodiment of the invention during the one injection phase into the injection mold and subsequent ver wetting or cooling phase already the plasticization for  the next injection process in the storage cylinder is successful This procedure completely reduces the cycle time considerably and thus increases the profitability of the Injection molding machine by increasing its productivity.

The invention is not restricted in its implementation to the preferred embodiment given above game. Rather, a number of variants are conceivable which of the solution shown also in principle makes use of different types.

Claims (20)

1. Method for intermittent injection molding of molded parts by means of a device for producing injection mold parts made of molding compound, consisting of

• - a screw cylinder with a screw conveyor for plasticizing the molding compound,
• - An injector with an injection cylinder and
• - An injection piston for transferring the plastifi ed molding compound in
• a mold in which the molding compound then polymerizes or crosslinks,

characterized,
that the plasticizing of the molding compound for the injection process of the subsequent work cycle already begins with implementation in a first receiving volume, while the injection process of the molding compound of the previous working cycle continues from a second receiving volume into the mold, whereby

• - either the two intake volumes are alternately filled and emptied into the mold in alternating work cycles during plastication, or
• - During the work cycle, a transfer of the molding compound from the first intake volume into the second volume takes place within a period that is short compared to the duration of the entire work cycle.

2. The method according to claim 1, characterized ge indicates that the first and the second Volume that alternately fills and into the shape be emptied, have different sizes. 3. The method according to any one of claims 1 or 2, characterized in that the injection process is carried out by superimposing two partial work cycles of successive work cycles, with the molding compound from the screw cylinder ( 5 ) with plasticization over at least one in in a first partial work cycle of the subsequent work cycle a first position valve ( 7 ) is transferred into a first injection cylinder having the first volume, while the plasticized molding compound already in a further, second volume, second injection cylinder is in a second partial working cycle of the previous working cycle via a further passage of the valve and the injection channel ( 8 ) is injected into the injection mold ( 9 ) and
that then - after moving the valve and closing the previously open passages - the plasticized molding compound from the first injection cylinder ( 1 ) through an then open and previously closed passage of the valve and the injection channel injected into the injection mold and then crosslinked and / or cooled there is, with the molding compound for the next working cycle from the screw cylinder via another then open and up to now closed passage of the valve in the second injection cylinder ( 3 ) is promoted. 4. The method according to claim 1, characterized in
that the injection process is carried out with superimposition of two partial work cycles of successive work cycles, the molding compound being plasticized by the screw conveyor in a first partial cycle of the work cycle following into one of the screw threads of the screw in the conveying direction behind the same, forming the first volume Free space of the cylinder surrounding the screw arrives, while the plasticized molding compound which is already located in a further injection cylinder having the second volume is injected into the injection mold ( 9 ) via the injection channel ( 8 ) in a second sub-work cycle of the preceding work cycle, a passage of a between which he most and the second volume arranged valve is closed ge
that then, after opening the valve, the content of the free space forming the first volume is transferred to the second volume. 5. The method according to claim 4, characterized ge indicates that the snail is filling of the free space forming the first volume - if necessary superimposed on the rotation of the screw, opposite for the direction of conveyance and after opening the valve according to Art a piston is pushed in the conveying direction. 6. The method according to claim 5, characterized ge indicates that the second volume around closing and in turn in the area of its outer surface Zy forming a piston within the injection cylinder linder limits the first volume, which during injection Process during the second sub-work cycle for injection ren the molding compound is reduced in the mold. 7. The method according to any one of the preceding claims, characterized in that the Vo lumina either according to the "last-in-first-out" principle or "First-in-first-out" to be filled and emptied the former case, the difference in the residence times of the he most and the last volume in volume elements to the difference between the times until the Form between the last one entering the volume though first emerging from this and first in this entering but last emerging volume element is fit. 8. The method according to any one of the preceding claims, characterized in that the  Molding compound to shorten the crosslinking time before transferring result in the mold being heated, each mold each an injection device is assigned. 9. The method according to claim 8, characterized ge indicates that the heating by means of a Shear cone takes place. 10. The method according to claim 9, characterized ge indicates that the injection speed speed of the molding compound depending on the optimal Er heating of the molding compound in the mold is variable. 11. Device for performing the method according to egg nem of the preceding claims, characterized, that at least two injection cylinders with corresponding Injection pistons are provided. 12. The apparatus according to claim 11, characterized in that the injection cylinders ( 1 ) and ( 3 ) with the injection pistons ( 2 ) and ( 4 ) via a Ven valve ( 7 ) with both the screw cylinder ( 5 ) and the injection mold ( 9 ) are connected via the injection channel ( 8 ). 13. The apparatus according to claim 12, characterized in that in one of the Ventilstellun gene the screw cylinder ( 5 ) with the injection cylinder ( 1 ) and at the same time the injection cylinder ( 3 ) with the injection mold ( 9 ) and in the other valve position the screw cylinder ( 5 ) with the injection cylinder ( 3 ) and at the same time connects the injection cylinder ( 1 ) with the injection mold ( 9 ) via the injection channel ( 8 ). 14. The apparatus according to claim 13, characterized ge indicates that the injection cylinder Volumes have a substantially matching size point. 15. The device according to one of claims 11 to 14, characterized in that plasti Molded compound between the injection cylinders is exchanged. 16. The apparatus according to claim 15, characterized in that a feed screw (10) is Gert in a storage cylinder (11) axially movable gela, the cylinder (11) is arranged as a piston in an injection cylinder (13) and Zvi as compound rule the cavity ( 19 ) in the storage cylinder ( 11 ) and the cavity ( 20 ) in the injection cylinder ( 13 ) has an opening in the bottom surface ( 15 ) of the storage cylinder, in which a check valve ( 12 ) is arranged. 17. The apparatus according to claim 16, characterized in that an outlet opening ( 14 ) in the Bo denfläche ( 16 ) of the injection cylinder is provided between the injection cylinder ( 13 ) and the injection mold for injecting the plasticized molding compound. 18. The apparatus according to claim 17, characterized in that an axially arranged groove ( 17 ) on the inside of the side wall of the injection cylinder ( 13 ) is embedded as a connection between the injection cylinder ( 13 ) and the injection mold for injecting the plasticized molding compound, one end of which is at the level of the bottom surface ( 16 ) of the injection cylinder and has a length which is greater than the maximum stroke length of the storage cylinder ( 11 ), and which at its bottom surface ( 16 ) opposite end in a bore ( 18 ) in the side wall of the injection cylinder opens, which in turn opens into the injection channel to the injection mold. 19. Device according to one of the preceding claims, characterized in that rule device for the pressure and / or the mass flow of the Molding compound is provided.