Portioning unit

Abstract

Portioning unit (1) which can be connected downstream in a compression molding machine to an outlet (3) of an extrusion unit (2) in order to receive plastic material from the extrusion unit (2) and to simultaneously separate several loads of a definable specific volume from it, wherein the portioning unit (1) comprises the following: a. a first chamber (4) which is connected to the extrusion unit (2) via a first valve (5), and b. a first piston (6) arranged in the first chamber (4), which is displaceable in a longitudinal direction of the first chamber (4) and is configured to receive a certain volume of plastic material from the extrusion unit (2) via the first valve (5); c. a second chamber (9) with an inlet opening (10) which is in fluidic communication with the first chamber (4) via a second valve (11) and which is configured to receive plastic material from the first chamber (4) through the second valve (11) and d. a second piston (12) which is displaceable in a longitudinal direction of the second chamber (9) in order to discharge the specific volume from the portioning unit (1) through an outlet opening (13) by moving the second piston (12) from an extended position (14) to a retracted position (15). e. several first housings (19) of charge separation units (18) for the simultaneous separation of several charges of plastic material through individual outlet openings (13), wherein each charge has a specific volume, are arranged parallel to one another, wherein the first housings (19) are each connected to a second housing (20) of a common supply block (21). f. wherein the second housing (20) of the supply block (21) is designed as a hot runner by comprising channels for distributing the plastic material taken up by the extruder (2) to the charge separation units (18), the material being kept in a paste-like form.

Description

AREA OF REVELATION

[0001] The present disclosure relates to a portioning unit suitable for a compression molding machine, a compression molding machine comprising such a portioning unit, and a method for operating such a portioning unit. BACKGROUND OF THE REVELATION

[0002] Devices for separating a continuous feed of plastic material from an extruder into individual batches of plastic material are well known. These batches of plastic material are typically fed into a mold for further processing, particularly in a (continuous) compression molding process. The plastic material is usually received by such devices in a paste-like form, i.e., in a state between solid and liquid.

[0003] Several attempts to provide such devices are known from the prior art and are briefly described below.

[0004] GB976615A, published in 1964 on behalf of Union Carbide Corp., relates to a device with molds having a plurality of cavities in conjunction with a number of dies fed by a single extruder. Laminates can be produced by inserting a disc or sheet of another material into the cavity of the mold before forming, or by placing the disc or sheet on the measured part, or by forming a first part, placing a disc on top of it, and forming a second part on top of the disc. Such laminates can be used as crown cap liners.

[0005] US6368094B1, published in 2002 on behalf of Alcoa Closure Systems, relates to an apparatus for feeding multiple molten plastic granules into cavities for compression molding the granules into bottle closures or bottle closure liners. The apparatus feeds molten plastic granules from a supply of molten plastic to a plurality of mold blocks, each mold block having a series of cavities. The mold blocks are transported on a rotating carousel. The apparatus includes a rotating multi-cutter with a plurality of cutting wings and a manifold block that receives the extruded plastic melt and directs it to a plurality of dies, each die being aligned with one or more of the cutting wings.The cutter blades extract a series of plastic granules from the plastic melt at the nozzles and convey the plastic granules into a series of cavities in a mold block. SUMMARY OF THE REVELATION

[0006] Known devices for separating a continuous feed of plastic material from an extruder into separate batches of plastic material have several disadvantages that prevent parallelization of the process. The aim of the present disclosure is to overcome at least one of these disadvantages.

[0007] In a preferred embodiment of the disclosure, a portioning unit in a compression molding machine is connected downstream of the outlet of an extrusion unit to receive plastic material from the extrusion unit and separate loads of a specific volume. However, other applications besides compression molding are also possible, such as blow molding or injection molding of thermoplastics or other materials.

[0008] The dispensing unit should be designed to enable uniform and repeatedly accurate dispensing of the plastic material into batches of a (definable) specific volume, especially if the dispensing unit includes multiple outlet openings designed to operate in parallel. Uneven dispensing of the plastic material should be avoided, particularly in applications where the dispensing unit must simultaneously divide the plastic material into multiple batches of a specific volume through separate outlet openings.

[0009] In general, the portioning unit according to the disclosure comprises a first chamber connected to the extrusion unit via a first valve. A first piston is arranged in the first chamber, which is displaceable in a longitudinal direction within the first chamber and is configured to receive a specific volume of plastic material from the extrusion unit through the first valve, specifically by moving the first piston from a retracted position to an extended position. Typically, a second chamber with an inlet opening, which is fluidically connected to the first chamber via a second valve, is configured to receive plastic material from the first chamber through the second valve.Typically, a second piston is arranged to be displaceable in the longitudinal direction of the second chamber in order to discharge the specified volume from the portioning unit through an outlet opening by moving the second piston from an extended position to a retracted position.

[0010] Preferably, the extended position of the first piston, in conjunction with the first chamber, defines the specific volume of the plastic material to be received by the extrusion unit per cycle. This allows for higher accuracy in the volume of the plastic material dispensed by the portioning unit per cycle compared to devices based on continuous extrusion of material that is periodically sheared by a cutting device to separate it into batches.

[0011] Depending on the design, the first and second pistons are arranged laterally spaced apart from each other. Alternatively, the first and second pistons can also be arranged coaxially. A coaxial arrangement allows for a more compact design, while a laterally separated arrangement enables a simpler construction.

[0012] Good results are possible if the first and / or second valve are designed as bolt valves, configured to open and close a material channel for the plastic material by moving a pin. Alternatively, the first piston forms part of the first valve. In this case, the first piston includes a first sealing surface for opening a first passage of the material channel connected to the first chamber. Optionally, the second piston can form part of the second valve. In this case, the second piston includes a second sealing surface for opening a second passage of the material channel connected to the second chamber.

[0013] In some variations, particularly when the first and second pistons are arranged coaxially, the first piston can have a pressure equalization channel that connects the first valve and the first chamber, at least temporarily, to prevent the first piston from shifting against a negative pressure (vacuum). The pressure equalization channel is preferably designed as a longitudinal groove on the outside of the first piston. The first piston can be rotatable about its longitudinal axis to temporarily connect and disconnect the first valve and the first chamber via the pressure equalization channel.

[0014] If present, the extended position of the first piston is defined by a mechanical end stop. The mechanical end stop preferably comprises a first stop surface that prevents the first piston from moving longitudinally along the first chamber when it is moved from the retracted position to the extended position. Typically, in the extended position, the first piston rests against the first stop surface of the mechanical end stop.

[0015] Good performance is possible if a second stop surface is positioned longitudinally along the first chamber, opposite the first stop surface. Typically, the first piston rests against the second stop surface in the retracted position.

[0016] In a preferred embodiment, the position of the mechanical end stop is adjustable in the longitudinal direction. This can be achieved, for example, by using washers of different heights (in the longitudinal direction) or different numbers of washers, if the first stop surface is located on a washer. However, other embodiments of the adjustable mechanical end stop are also possible, such as height-adjustable detent mechanisms or similar designs.

[0017] Depending on the application, the portioning unit comprises at least one charge separation unit with a first housing that is fluidically connected downstream to a second housing of a supply block. Typically, the second housing of the supply block is fluidically connected downstream to an outlet of an extrusion unit. Particularly in applications requiring the simultaneous feeding of multiple charges of plastic material, the portioning unit preferably comprises several first housings of charge separation units arranged in parallel for the substantially simultaneous separation of multiple charges of plastic material, each with a specific volume, wherein the first housings are each connected to a second housing of a common supply block.The second housing of the supply block is preferably designed as a hot runner system, comprising channels for distributing the plastic material taken up by the extruder to the charge separation units, the material being kept in a paste-like form. For this purpose, the second housing can include at least one heating element.

[0018] Good results can be achieved if the first housing of the charge separation unit is multi-part, allowing for a modular design. Preferably, the first housing of the charge separation unit comprises a first block containing the first chamber and a second block containing the second chamber, which is fluidically and thermally connected to the first block. If present, a sleeve seals the fluid connection between the first and second blocks by pressing corresponding sealing surfaces of the sleeve and the first and second blocks, respectively, against each other.

[0019] If the first valve is designed as a separate element, a third block can accommodate the first valve, which is fluidically connected upstream to the first block.

[0020] For precise dispensing of a batch of plastic, the second piston can include an air line terminating in an end face of the second piston to pneumatically separate the plastic from the portioning unit during dispensing. This eliminates the need for an additional, separate cutting device known from the prior art.

[0021] To ensure proper discharge of the plastic material, the diameter of the second piston is equal to the diameter of the outlet opening. This allows the second piston to eject all the plastic material into the second chamber, so that over a longer period (multiple cycles) essentially no material remains in the second chamber. This minimizes the potential for thermal degradation of the plastic.

[0022] At least one actuator is provided to actuate the pistons of the portioning unit. In a preferred embodiment, the first piston is connected to a first actuator for moving the first piston between the extended and retracted positions. Furthermore, the second piston is typically connected to a second actuator for moving the second piston longitudinally within the second chamber. In the case of multiple charge separation units, a common first actuator can actuate two or more first pistons. Similarly, a common second actuator can actuate two or more second pistons. However, individual first and second actuators per charge separation unit are also possible. Depending on the application, the first and / or second actuator may be a hydraulic, pneumatic, or electric actuator.

[0023] In some variants, the portioning unit is at least partially manufactured using an additive process; in particular, the supply block is manufactured using an additive process.

[0024] Another aspect of the disclosure relates to a device for compression molding, comprising at least one portioning unit, as described in more detail above and below.

[0025] The portioning unit according to the disclosure is suitable for separating a variety of different materials in various states into charges of specific volume. The state of the material can be solid or liquid, in particular pasty or plastic. The material can be a polymeric or plastic material, especially a thermoplastic material. However, other materials are also possible, such as paper pulp, wood fiber material, or plant fiber material (e.g., wheat).

[0026] Another aspect of the disclosure relates to a method for operating a portioning unit as described above. The described embodiments of the portioning unit can serve to carry out the method according to the disclosure.

[0027] In a preferred embodiment, the method comprises the steps of opening the first valve; receiving a certain volume of plastic material from the extrusion unit into the first chamber; closing the first valve and opening the second valve; moving the first piston from the retracted position to the extended position, thereby pushing plastic material from the first chamber into the second chamber; and moving the second piston from the retracted position to the extended position, thereby pushing plastic material through the outlet opening.

[0028] The embodiment of the method for operating a portioning unit described above also discloses correspondingly designed embodiments of the portioning unit and vice versa.

[0029] It is understood that both the preceding general description and the following detailed description represent embodiments and serve to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings serve to further understanding and are an integral part of this description and are incorporated therein. The drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the disclosed concepts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The disclosure described herein will be better understood from the detailed description below and the accompanying drawings, which should not be considered as limiting the disclosure described in the accompanying claims. The drawings show: Fig. 1 a partially cutaway view of a first variant of a portioning unit according to the disclosure; Fig. 2 a sectional view of the first variant of Fig. 1, represented by the section line LL; Fig. 3 a perspective view of a second variant of a portioning unit according to the revelation; Fig. 4 a sectional view of the second variant of Fig. 3, which is marked by the intersection line NN; Fig. 5 a perspective view of a third variant of a portioning unit according to the revelation; and Fig. 6 a sectional view of the third variant of Fig. 5, which is marked by the intersection line ○○. DESCRIPTION OF THE EXECUTION FORMS

[0031] Reference is now made in detail to specific embodiments, examples of which are shown in the accompanying drawings, which illustrate some, but not all, of their features. Indeed, the embodiments disclosed herein can be embodied in many different forms and should not be interpreted as being limited to those set forth herein; rather, these embodiments are provided so that this disclosure satisfies applicable legal requirements. Wherever possible, the same reference numbers are used to refer to identical components or parts.

[0032] Fig. Figure 1 shows a partial sectional view of a first variant of a portioning unit 1 according to the disclosure and Fig. 2 shows a sectional view of the first variant of Fig. 1, which is marked by the intersection line LL. Fig. Figure 3 shows a perspective view of a second variant of a portioning unit 1 according to the revelation and Fig. 4 a sectional view of the second variant indicated by the section line NN Fig. 3. Fig. Figure 5 shows a perspective view of a third variant of a portioning unit 1 according to the revelation, and Fig. Figure 6 shows a sectional view of the third variant of Fig. 5, which is marked by the intersection line ◯◯.

[0033] The variants of the portioning unit 1 are connected downstream to an outlet 3 of an extrusion unit 2 in order to receive plastic material from the extrusion unit 2, as shown in the Fig. 3 and Fig. Figure 4 is shown (not shown for the first and third variants). The portioning unit 1 separates the plastic material taken up by the extrusion unit 2 into separate loads of a specific volume. These loads are typically supplied directly to a mold 31 of a molding press (not shown) or indirectly via a transfer device 31 for further processing.

[0034] The variants shown generally include a first chamber 4 and a second chamber 9 to separate the plastic material into charges. The first chamber 4 is, as shown in Fig. As shown in Figure 4, the first chamber 4 is connected to the extrusion unit 2 via a first valve 5. The second chamber 9 is typically connected to the first chamber 4 via an inlet opening 10 through a second valve 11. This allows for the selective transport of plastic material between the first and second chambers 4, 9. As shown, a first piston 6 is arranged to be displaceable in a longitudinal direction z of the first chamber 4. The first chamber 4 is designed such that, when the first valve 5 is open, it receives the specific volume of plastic material from the extrusion unit 2. In the second variant, as shown in Figure 4, the first chamber 9 is connected to the extrusion unit 2 via a first valve 5. Fig. 3 and Fig. As shown in Figure 4, the first piston 6 is moved from the retracted position 7 to the extended position 8, while the plastic material flows into the first chamber 4 due to the pressure generated by the extrusion unit 2.

[0035] In the first and third variants, as in the Fig. 1, Fig. 2 and Fig. 5, Fig. As shown in Figure 6, the first piston 6 is moved from the retracted position 7 to the extended position 8 by a first actuator 27 connected to the first piston 6 before the plastic material is received.

[0036] A second piston 12 is usually arranged to be displaceable in a longitudinal direction z of the second chamber 9 in order to discharge the specific volume from the portioning unit 1 through an outlet opening 13 by moving the second piston 12 from an extended position 14 to a retracted position 15.

[0037] In the first variant, as in the Fig. 1 and Fig. As shown in Figure 2, the first and second pistons 6, 12 are arranged coaxially. The first piston 6 is hollow to accommodate the second piston 12. The first and second pistons 6, 12 are generally arranged to move independently of each other. A similar coaxial arrangement is implemented in the third variant, as shown in Figure 2. Fig. 6 is the easiest to recognize.

[0038] The second variant, which is in the Fig. 3 and Fig. As can be seen in Figure 4, the first and second pistons 6, 12 are arranged laterally spaced apart from each other. Here, the first valve 5 is designed as a needle valve 5, which opens and closes a material channel 33 for the plastic material by moving its needle.

[0039] As described in the first and third variants, the first valve can also be partially formed by the first piston 6. In this case, an outer surface of the first piston 6 opens and closes a passage of the material channel 33, as best illustrated in Fig. 6 can be seen. The second valve 11 is usually formed by the second piston 12, as in Fig. 1 is shown, in a similar manner to the first piston. In this case, the second piston 12 includes an outer surface or outer edge that serves as a sealing means for opening and closing a passage to the second chamber 9.

[0040] To define the specific volume of plastic material to be received by the extrusion unit 2 per cycle, the extended position 8 of the first piston 6 is defined by a mechanical end stop 16 with a first stop surface 17. The first stop surface 17 prevents movement of the first piston 6 in the longitudinal direction z of the first chamber 4 when the first piston 6 is moved from the retracted position 7 to the extended position 8. A second stop surface 32 is typically arranged in the longitudinal direction z opposite the first stop surface 17 to limit the movement of the first piston 6 in the longitudinal direction z of the first chamber 4 when the first piston 6 is moved from the extended position 8 to the retracted position 7. The first and second stop surfaces 17 and 32 are best positioned in Fig. 2 to recognize.

[0041] As in the Fig. 3 and Fig. As shown in Figure 4, the portioning unit 1 typically comprises at least one charge separation unit 18 with a first housing 19 connected upstream to a second housing 20 of a supply block 21. The supply block 21 is fluidically connected downstream of the outlet 3 of the extrusion unit 2. In the variants shown, the first housing 19 of the charge separation unit 18 comprises a first block 22, in which the first chamber 4 is housed, and a second block 23, in which the second chamber 9 is housed, which is fluidically and thermally connected to the first block 22. The second variant additionally comprises a third block 24, which is fluidically connected upstream to the first block 22 and houses the first valve 5, in this case a separate needle valve 5.The plastic material flows from outlet 3 through supply block 21 (via the third block 24) into the first chamber 4 in the first block 22 and from there into the second chamber 9 in the second block 23, from where it is discharged via outlet opening 13.

[0042] Unlike the first and second variants, the third variant, as in Fig. Figure 5 shows several parallel first housings 22 of charge separation units 18, which are connected to a second housing 20 of a common supply block 21.

[0043] As in Fig. As can be seen best in Figure 4, the second piston 12 can include an air line 25 that terminates in an end face 26 of the second piston 12 to pneumatically separate the plastic material from the portioning unit 1 when dispensing a load.

[0044] For clean discharge of the plastic from the outlet opening 13, the diameter 29 of the second piston 12 is equal to the diameter 30 of the outlet opening 13, as shown in Fig. 2 shown.

[0045] In the illustrated variant, the first piston 6 is connected to a first actuator 27, which moves the first piston 6 between the extended position 8 and the retracted position 7. Furthermore, the second piston 12 is connected to a second actuator 28, which moves the second piston 12 between the retracted and extended positions 15, 14. The actuators 27, 28 shown here are pneumatic. The wave-shaped indentation visible in the first and second actuators 15 indicates that the part has been reduced in size for illustrative purposes. An exemplary sequence of positions 7, 8, 14, 15 of the first and second pistons 6, 12 within a cycle for supplying a load of plastic material in a mold 31 is shown in Fig. Shown from left to right in 6 places.

[0046] Rather, the words used in the description are descriptive rather than restrictive, and it is understood that various modifications may be made without deviating from the scope of the revelation. LIST OF TERMS 1 portioning unit 2 extrusion units 3 Outlet (extrusion unit) 4 First Chamber 5 First valve 6 First piston 7 Retracted position (first piston) 8 Extended position (first piston) 9 Second Chamber 10 Entrance opening 11 Second valve 12 Second piston 13 Outlet opening 14 Extended position (Second piston) 15 Retracted position (second piston) 16 Mechanical end stop 17 First stop surface 18 charge separation unit 19 First case 20 Second case 21 Supply block 22 First block (first housing of the charge separation unit) 23 Second block (first housing of the charge separation unit) 24 Third Block 25 Air line (second piston) 26 Front surface (Second piston) 27 First actuator (first piston) 28 Second actuator (second piston) 29 diameter (second piston) 30 mm diameter (outlet opening) 31 Form / Transport device 32 Second stop surface 33 Material channel QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] GB 976615A

[0004] US 6368094B1

[0005]

Claims

[1] Portioning unit (1) which can be connected downstream of an outlet (3) of an extrusion unit (2) in a compression molding machine in order to receive plastic material from the extrusion unit (2) and to simultaneously separate several loads of a definable specific volume from it, wherein the portioning unit (1) comprises the following: a. a first chamber (4) which is connected to the extrusion unit (2) via a first valve (5), and b. a first piston (6) arranged in the first chamber (4), which is displaceable in a longitudinal direction of the first chamber (4) and is configured to receive a certain volume of plastic material from the extrusion unit (2) via the first valve (5); c. a second chamber (9) with an inlet opening (10) which is in fluidic communication with the first chamber (4) via a second valve (11) and which is configured to receive plastic material from the first chamber (4) through the second valve (11) and d. a second piston (12) which is displaceable in a longitudinal direction of the second chamber (9) in order to discharge the specific volume from the portioning unit (1) through an outlet opening (13) by moving the second piston (12) from an extended position (14) to a retracted position (15). e. several first housings (19) of charge separation units (18) for the simultaneous separation of several charges of plastic material through individual outlet openings (13), wherein each charge has a specific volume, are arranged parallel to one another, wherein the first housings (19) are each connected to a second housing (20) of a common supply block (21). f. wherein the second housing (20) of the supply block (21) is designed as a hot runner by comprising channels for distributing the plastic material taken up by the extruder (2) to the charge separation units (18), the material being kept in a paste-like form. [2] The portioning unit (1) according to claim 1, wherein the first piston (6) and the second piston (12) are arranged laterally spaced apart from each other or the first piston (6) and the second piston (12) are arranged coaxially to each other. [3] Portioning unit (1) according to at least one of the preceding claims, wherein the first piston (6) forms part of the first valve (5). [4] Portioning unit (1) according to at least one of the preceding claims, wherein the second piston (12) forms part of the second valve (11). [5] Portioning unit (1) according to at least one of the preceding claims, wherein the extended position of the first piston (6) is defined by a mechanical end stop (16). [6] The portioning unit (1) according to claim 5, wherein a position of the mechanical end stop (16) is adjustable in the longitudinal direction. [7] The portioning unit (1) according to at least one of the preceding claims, wherein the first housing (19) of the charge separation unit (18) comprises: a. a first block (22) that houses the casing of the first chamber (4), and b. a second block (23) which houses the second chamber (9) and is fluidically and thermally connected to the first block (22). [8] The portioning unit (1) according to claim 7, wherein a third block (24) is fluidically connected upstream to the first block (22) and accommodates the first valve (5). [9] Portioning unit (1) according to at least one of the preceding claims, wherein the second piston (12) comprises an air line (25) which terminates in an end face (26) of the second piston (12) to pneumatically separate the plastic material from the portioning unit (1) during dispensing. [10] Portioning unit (1) according to at least one of the preceding claims, wherein the first piston (6) is connected to a first actuator (27) for moving the first piston (6) between the extended position and the retracted position and the second piston (12) is connected to a second actuator (28) for moving the second piston (12). [11] Portioning unit (1) according to at least one of the preceding claims, wherein the portioning unit (1) is at least partially produced by an additive process, in particular the supply block (21) is produced by an additive process. [12] Portioning unit (1) according to at least one of the preceding claims, wherein a diameter (29) of the second piston (12) is equal to a diameter (30) of the outlet opening (13). [13] Portioning unit (1) according to at least one of the preceding claims, wherein a common first actuator (27) can actuate two or more first pistons (6) and / or a common second actuator (28) can actuate two or more second pistons (12). [14] A device for compression molding comprising a portioning unit (1) connected downstream to an outlet (3) of an extrusion unit (2) to receive plastic material from the extrusion unit (2) and simultaneously separate several loads of a definable specific volume and provide the loads in molds (31), the portioning unit (1) comprising: a. a first chamber (4) which is connected to the extrusion unit (2) via a first valve (5), and b. a first piston (6) arranged in the first chamber (4), which is displaceable in a longitudinal direction of the first chamber (4) and is configured to receive a certain volume of plastic material from the extrusion unit (2) via the first valve (5); c. a second chamber (9) with an inlet opening (10) which is in fluidic communication with the first chamber (4) via a second valve (11) and which is configured to receive plastic material from the first chamber (4) through the second valve (11) and d. a second piston (12) which is displaceable in a longitudinal direction of the second chamber (9) to discharge the specific volume from the portioning unit (1) through an outlet opening (13) by moving the second piston (12) from an extended position (14) to a retracted position (15), wherein a diameter (29) of the second piston (12) is equal to a diameter (30) of the outlet opening (13); e. several first housings (19) of charge separation units (18) for the simultaneous separation of several charges of plastic material through individual outlet openings (13), wherein each charge has a specific volume, are arranged parallel to one another, wherein the first housings (19) are each connected to a second housing (20) of a common supply block (21). f. wherein the second housing (20) of the supply block (21) is designed as a hot runner by comprising channels for distributing the plastic material taken up by the extruder (2) to the charge separation units (18), the material being kept in a paste-like form. [15] Portioning unit (1) which can be connected downstream to an outlet (3) of an extrusion unit (2) in a compression molding machine in order to receive plastic material from the extrusion unit (2) and to simultaneously separate several loads of a certain volume from it, wherein the portioning unit (1) comprises the following: a. a first chamber (4) which is connected to the extrusion unit (2) via a first valve (5), and b. a first piston (6) arranged in the first chamber (4), which is displaceable in a longitudinal direction of the first chamber (4) and is configured to receive a certain volume of plastic material from the extrusion unit (2) via the first valve (5); c. a second chamber (9) with an inlet opening (10) which is in fluidic communication with the first chamber (4) via a second valve (11) and which is configured to receive plastic material from the first chamber (4) through the second valve (11) and d. a second piston (12) which is displaceable in a longitudinal direction of the second chamber (9) in order to discharge the specific volume from the portioning unit (1) through an outlet opening (13) by moving the second piston (12) from an extended position (14) to a retracted position (15). [16] The portioning unit (1) according to claim 15, wherein several first housings (19) of charge separation units (18) for the simultaneous separation of several charges of plastic material through individual outlet openings (13), each charge having a specific volume, are arranged parallel to one another, wherein the first housings (19) are each connected to a second housing (20) of a common supply block (21). [17] The portioning unit (1) according to claim 16, wherein the second housing (20) of the supply block (21) is designed as a hot runner by comprising channels for distributing the plastic material received by the extruder (2) to the charge separation units (18), wherein the material is kept in a paste-like form. [18] The portioning unit (1) according to at least one of the preceding claims 15 to 17, wherein the first piston (6) and the second piston (12) are arranged laterally spaced apart from each other. [19] Portioning unit (1) according to at least one of the preceding claims 15 to 18, wherein the second piston (12) comprises an air line (25) which terminates in an end face (26) of the second piston (12) to pneumatically separate the plastic material from the portioning unit (1) during dispensing. [20] Portioning unit (1) according to at least one of the preceding claims 15 to 19, wherein a diameter (29) of the second piston (12) is equal to a diameter (30) of the outlet opening (13). [21] Portioning unit (1) according to at least one of the preceding claims 15 to 20, wherein the first piston (6) forms part of the first valve (5). [22] Portioning unit (1) according to at least one of the preceding claims 15 to 21, wherein the second piston (12) forms part of the second valve (11). [23] Portioning unit (1) according to at least one of the preceding claims 15 to 22, wherein the extended position of the first piston (6) is defined by a mechanical end stop (16).

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