DE102012104251A1 - Method for energy recovery in apparatus for molding of plastics, involves storing mechanical energy during movement for closing or opening of molding unit during deceleration of moving tool halves, and relaxation of clamping force - Google Patents

Abstract

The method involves storing the mechanical energy during the movement for closing or opening of a molding unit during the deceleration of the moving tool halves, and relaxation of the clamping force in the uncoupling of the tool halves in a hydraulic accumulator in a temporary manner. A hydraulic drive (4) is supplied for a molding operation. The hydraulic drive is used with a process cylinder with pressure medium chambers for moving the movable tool halves. The pressure medium chambers are separated by a process piston. An independent claim is included for a device with a storage container.

Description

The invention relates to a method for energy recovery in a device for molding plastics, preferably in a molding apparatus comprising a molding unit with a stationary mold half and a movable mold half, which are coupled to form a forming cavity, and a hydraulic drive for the movable Includes tool half and a feed unit for a liquefied molding material in the forming cavity, and the device as such.

In the production of molded parts of plastics devices are used which on the one hand can have a stationary mold half and the other a movable mold half. The two tool halves form a cavity which describes the form to be formed. A plastic to be injected into this cavity is first liquefied using high energy and injected under pressure into this cavity.

In such an injection molding machine, a high pressure for molding the resin is generated in the apparatus, whereby the pressure for shaping during injection and in the holding pressure phase is built up by the plasticizing unit to form the molding. In this case, a hydraulic counterforce, the s.g. Closing force built. Alternatively, toggle units are used in electrically mechanically driven injection molding machines. An assembly of such an injection molding machine as a device for shaping plastics, which is basically known in the prior art, is the closing unit, which is frequently to be found in the region of large closing forces as a two-plate closing unit.

In such a 2-plate clamping unit are provided on a machine bed, a fixed platen with one mold half and a movable movable platen with the other mold half. In one of the platens may be provided columns which extend to the opposite mold mounting plate and enforce this at least in the closed state of the clamping unit. Furthermore, locking devices and means for generating a closing force are provided. Such 2-plate clamping units are known in various embodiments from the prior art ( Johannaber / Michaeli, "Handbook Injection Molding", Hanser 2001, pages 836-839 ).

As a result, a considerable amount of energy is required in this type of molding production. On the one hand, the plastic must first be liquefied and, on the other hand, a high pressure must be built up. To save energy, it is known in the cooling of the plastic or hydraulic oil according to the DE 10 2010 049 969 A1 to absorb the released heat energy and return it to the process. Such a so-called recuperation method makes it possible to reduce the power consumption of such a device. However, a substantial proportion of the total energy requirement represents the drive energy required to operate the axles.

For example, in such a device for producing molded parts, a closing force of up to 40,000 kN may be necessary, with an elastic deformation of up to 4 to 5 mm being produced as a function of the closing force and the rigidity of the closing unit or of the injection molding tool used. When closing the device masses are moved between 30 and 100 tons, with a speed of 0.6 to 1 m / s. The cycle times range from 4 to 60 sec. This results in a potential energy saving of 10 to 50,000 kilowatt hours per year.

In the current state of the art, the illustrated forms of energy are dissipated when relaxing the deformed components and when braking the moving masses. This raises the task of making available for the cycle applied drive power in the molding production again to reduce the overall energy needs on.

According to the invention, this object is achieved in that an existing in the plant mechanical energy during the deceleration of the at least one movable mold half during the closing movement and / or relaxation of the closing force and / or during decoupling of the tool halves in at least one hydraulic accumulator during an injection cycle and at least one pressure element can be supplied during a next injection molding cycle for pressure buildup.

Further advantageous embodiments of the invention will become apparent from the dependent claims.

The advantage of this method over the prior art is that the energy consumption in the production of molded parts can be reduced. Here, the mechanical energy present in the hydraulic drive can be traced back. Thus, in an embodiment of the method according to the invention when closing the device, the movable mold half by means of a Verfahrzylinders moved to the stationary mold half, or in a further embodiment of the method according to the invention, the movable mold half using a Verfahrzylinders of the stationary mold half separated and moved into the opening position.

Damage to the tool halves must be avoided, and for this purpose, the movable mold half must be braked and brought to a standstill before reaching the closed position or the open position. The thereby moved, sometimes very large elements with a weight of up to 100 tons are equipped with a high kinetic energy. When braking the movable mold half, this mechanical energy is released. For this purpose, according to the invention in the hydraulic drive of the device at least one hydraulic accumulator is used for braking the movable mold half, in which the discharged from the pressure medium space in the displacement cylinder pressure medium is passed against the existing internal pressure in the hydraulic accumulator. In this case, an increasing back pressure is built up in the hydraulic accumulator, which causes the movable mold half to be braked. As the back pressure increases, the speed of the movable mold half and the kinetic energy contained therein decrease. This energy is temporarily stored in the form of increased pressure in at least one hydraulic accumulator.

In a further embodiment, the invention provides that the shaping device comprises two movable tool halves, which are moved towards one another and coupled to one another for forming the shaping cavity and are decoupled after the end of the shaping operation and moved to the opening position in which the shaped piece is removed from the shaping unit can be.

Furthermore, the method according to the invention provides that the energy stored temporarily in the at least one hydraulic accumulator during the injection molding cycle is returned to at least one pressure element, such as a displacement cylinder or a pressure pad, and thus used to drive the movable plate of the clamping unit. As a result, less energy must be expended to pressurize the respective pressure element with the necessary pressure for the application of the device. However, the cached in the hydraulic accumulator pressure is usually not enough for the next molding process. In order to build up the pressure necessary in the hydraulic accumulator, a pump unit for increasing the hydraulic pressure in the hydraulic drive and hydraulic accumulator can additionally be present, which can increase the pressure in the hydraulic accumulator before, during or between molding production. In this case, a plurality of hydraulic accumulators can be acted upon by a pump unit with the necessary pressure at the same time. The pump unit is thus used more efficiently and leads to a further saving of energy.

In the case of the relaxation of the elastically deformable components of the closing unit, according to the invention, the energy thus released can likewise be temporarily stored in a hydraulic accumulator. The energy released during the relaxation of the closing force during the decoupling of the tool halves is diverted via the hydraulic drive to a hydraulic accumulator, into which the pressure medium discharged from the pressure medium chamber in the pressure pad is directed against the existing internal pressure in the hydraulic accumulator Hydraulic accumulator, while reducing the pressure within the pressure element. Thus, the energy present in the pressure element can be temporarily stored in the hydraulic accumulator. In a next molding process, less pressure is needed to charge the pressure element using the hydraulic accumulator accordingly for the necessary closing force of the device. This saves a substantial part of the energy for the application of the device.

In a further advantageous embodiment, it is provided that at least two hydraulic accumulators preferably pressure alternately Verfahrzylinder for opening and closing the movable mold half and mechanical energy is stored in a braking of the moving mold half in a hydraulic accumulator and at least two more hydraulic accumulators are used to pressurize the pressure pad , wherein at least one hydraulic accumulator is used to build up the closing pressure and the other is used for temporarily storing the released during the relaxation of the pressure pad mechanical energy.

Furthermore, the invention also relates to the device for shaping plastics provided, wherein at least one hydraulic accumulator is provided, which is connected via at least one valve with at least one pressure element. In this case, the hydraulic accumulator can be used on the one hand to store the released during the deceleration of the movable plate and / or during the relaxation of the pressure pad mechanical energy between. On the other hand, the hydraulic accumulator can also be used to apply the pressure element accordingly with the necessary initial pressure. The hydraulic accumulator can also serve only for the pressurization example of a pressure pad. In this case, a Einwege- or check valve can be used as a valve to compensate for the pressure in one direction only. For example, when relaxing the pressure pad, it becomes another one Hydraulic accumulator used for temporary storage of the released mechanical energy. Accordingly, certain hydraulic accumulators may be provided for different tasks in the apparatus or method. In the normal case, however, the hydraulic accumulator is connected to a two-way valve with at least one of the pressure elements.

In an advantageous embodiment, the device provides that the at least one hydraulic accumulator via a pump valve, preferably a one-way valve is connected to at least one pump unit, which can be acted upon by the hydraulic accumulator with pressure and / or pressure medium. The hydraulic accumulator can be used, inter alia, to pressurize the pressure elements. The pressure in the hydraulic accumulator must be increased again to the necessary pressure after each shaping process. For this purpose, the hydraulic accumulator is connected to the pump unit via a one-way valve. The one-way valve allows the pressure compensation only from the pump unit to the hydraulic accumulator and not in the other direction. The big advantage of using a central pump unit is that it can be used much more efficiently. Alternatively, a respective pump unit must be provided for the application of the pressure elements. When using only one pump unit and a pressurization via the hydraulic accumulator energy is additionally saved.

In addition, the pump unit advantageously has a reservoir, which is filled with a pressure-transmitting medium (pressure medium) and / or at least one pressure element is connected via a circulation valve with an inlet of a reservoir. The reservoir serves to provide the pressure-transmitting medium for the system. It may happen that not all elements of the device are pressurized and additionally pressure-transmitting medium must be provided at a pressurization. It can be removed using the pump unit and the circulation valve as a medium from the reservoir and fed into the device.

In a further advantageous embodiment of the device according to the invention, the pressure element is connected via a recuperation with at least one hydraulic accumulator. During deceleration of the movable plate and / or during the relaxation of the pressure pad, the corresponding recuperation valve is opened, whereby the pressure can flow into the hydraulic accumulator and builds up there as a back pressure. As a result, the energy stored in the device according to the invention can be temporarily stored in the hydraulic accumulator with the aid of the recuperation valve.

To achieve the required traversing speeds, tractors with a relatively small piston diameter are used as traversing cylinders. To build the closing force Kraftaktoren be used with a relatively large diameter to reach the required closing forces with moderate pressures.

Furthermore, the pressure element, such as a Verfahrzylinder, connected via a central valve with the at least one valve to the hydraulic accumulator. The central valve of the pressure cylinder allows on the one hand to switch from a closing movement into an opening movement and in each case alternately to use a hydraulic accumulator for intermediate storage of the thereby released mechanical energy. In addition, the central valve also allows a holding position, which is taken during the shaping.

A further advantageous embodiment is that the recuperation valves are connected to each other via lines. Thus, the respective hydraulic accumulator required for temporary storage of mechanical energy can be used.

In a further advantageous embodiment, the device provides a hydraulic drive and at least two hydraulic accumulator, which alternately pressurize a pressure cylinder for opening and closing the movable mold half and caching the mechanical energy during braking of the movable mold half by pressurizing a hydraulic accumulator and continue at least one Hydraulic accumulator is provided for pressurizing a pressure pad and to build a closing pressure and at least one further hydraulic accumulator is provided for temporarily storing the released mechanical energy during the relaxation of the pressure pad.

• – der Verfahrzylinder zum Verfahren der beweglichen Platte über einen Abschnitt des Verfahrweges der beweglichen Platte ausgebildet ist,
• – beide Seiten des Verfahrkolbens in dem Verfahrzylinder mit einem Druckmittel beaufschlagbar sind, so dass der Verfahrkolben innerhalb des Verfahrzylinders und relativ zu diesem und zur feststehenden Platte sowohl in Schließrichtung als auch in Öffnungsrichtung über einen Abschnitt des Verfahrweges mit der Verfahrkolbenstange und der beweglichen Platte verfahrbar ist
• – jedem Druckmittelraum im Verfahrzylinder mindestens ein Hydraulikspeicher zugeordnet ist, der mit dem Druckmittelraum in ventilgesteuerter Hydraulikverbindung steht,
• – und eine Regelungseinheit zum Betreiben der hydraulische Antriebe und Ventile vorgesehen ist,

In one embodiment, the invention thus relates to a closing unit for an injection molding machine, in particular a 2-plate closing unit for an injection molding machine, with a fixed plate, a movable plate, at least one drive for moving the movable plate via a travel path when approaching and when driving Closing unit, with at least one stored in a guide Verfahrkolbenstange which is connected to a Verfahrkolben in Verfahrzylinder on the fixed plate, and wherein the guide of the Verfahrkolbenstange on the movable plate is assigned in each case a locking device whose locking elements with the associated Guide is engageable to form a locked state

• The movement cylinder is designed for moving the movable plate over a section of the travel path of the movable plate,
• - Both sides of the Verfahrkolbens in the Verfahrzylinder be acted upon with a pressure medium, so that the Verfahrkolben is movable within the Verfahrzylinders and relative to this and the fixed plate both in the closing direction and in the opening direction over a portion of the travel path with the Verfahrkolbenstange and the movable plate
• Each pressure medium space in the displacement cylinder is assigned at least one hydraulic accumulator which is in valve-controlled hydraulic connection with the pressure medium space,
• And a control unit is provided for operating the hydraulic drives and valves,

In one embodiment of the device according to the invention, in addition to or as an alternative to the hydraulic accumulator which is in valve-controlled hydraulic connection with the pressure medium chamber in the displacement cylinder, at least one hydraulic accumulator communicating with the pressure medium space in the pressure pad 6 is in valve-controlled hydraulic connection, be provided.

Preferably, the device provides a hydraulic drive and at least two hydraulic accumulator, which apply alternately pressure medium spaces in Verfahrzylinder a pressure cylinder for opening and closing the movable mold half with pressure and caching during braking of the movable mold half by pressurizing a hydraulic accumulator, the mechanical energy and continue at least a hydraulic accumulator is provided for pressurizing a pressure pad and at least one further hydraulic accumulator is provided for temporarily storing the released mechanical energy during the relaxation of the pressure pad.

The invention will be further illustrated by the following figures. Showing:

1 the schematic structure of a two-plate locking unit in the open state;

2 the schematic structure of a two-plate clamping unit in the closed state;

3 the basic structure of a two-plate closing unit operated according to the invention; and

4 the schematic structure of the valve positions.

The hydraulic connection between the control unit used according to the invention and the two-plate clamping unit is realized via standard hydraulic lines, which in the 1 and 2 are schematically indicated by the positions A1, A2 and A3.

As in 1 and 2 is shown, the basic structure of a two-plate clamping unit in the open state with the movable plate 2 and the fixed plate 3 shown. The injection mold has the negative mold halves 1a and 1b on that the negative mold 1 form the component to be produced. At the beginning of the injection cycle, the movable plate 2 the open clamping unit at a high speed in the direction of the stationary plate 3 moves until the contact between the two female mold halves 1a . 1b of the injection mold is made. For hydraulic drive of the movable plate 2 become traversing cylinders 4a , Traversing piston 4b and travel piston guide 4c used. After closing the injection mold 1 becomes the movable plate 2 with the aid of profiled slides that can be moved radially to the longitudinal axis of the traversing cylinder 5 in the axial direction on the travel piston guides 4c locked.

In the next step, the closing force with the help of the pressure pad 6 hydraulically constructed. The plasticized plastic granulate is used for molding as a molding compound in the cavity between the female mold halves 1a and 1b injected by means of the plasticizing unit, not shown. The over the pressure pad 6 applied closing force is required to the parting line in the injection mold between the female mold halves 1a and 1b To seal at the high pressures occurring.

For a better overview, the clamping unit is in 2 shown in the closed state. The item numbers are identical to 1 ,

In 3 The hydraulic circuit for recuperation of the kinetic energy and the spring energy is shown schematically. Here are in 3 the traversing cylinders 4a the two-plate clamping unit schematically by a differential cylinder 7 played. The exemplary four pressure pads 6 a two-plate clamping unit are schematically represented by a spring-returnable cylinder 8th shown. The spring of the spring-returnable cylinder 8th should symbolize the elastic behavior of the tool and the positioning cylinder of the clamping unit graphically.

The drive power at the actuators A1, A2 and A3 is exclusively from hydraulic accumulators 9 . 10 . 11 . 12 provided. In order to avoid electrical load peaks on the drive, this works in a constant throughout the cycle ' Operating point. This operating point can be chosen so that no more power is provided by the drive than is required by the axes. The interface designations for the actuators A1, A2 and A3 in 3 are identical to the interface designations A1, A2 and A3aus den 1 and 2 ,

• – einem Hydraulikspeicher 9, 10, 11, 12,
• – einem Wegeventil zur Ansteuerung der jeweiligen Aktorfunktion, im Folgenden Aktionsventil 13, 14, 15, 16 genannt,
• – einem Wegeventil zum Aufladen des Hydraulikspeichers mit der vom Antrieb bereit gestellten Energie, im Folgenden Ladeventil 17, 18, 19, 20 genannt, und
• – einem Wegeventil zur Steuerung der Rekuperationsfunktion, im Folgenden Rekuperationsventil 21, 22, 23, 24 genannt.

In the 3 illustrated control unit can be divided into individual areas via four nodes K1, K2, K3 and K4. In each node again run four lines together. These are each the supply line to:

• - a hydraulic accumulator 9 . 10 . 11 . 12 .
• - A directional control valve for controlling the respective actuator function, hereinafter action valve 13 . 14 . 15 . 16 called,
• - A directional control valve for charging the hydraulic accumulator with the energy provided by the drive, hereinafter charging valve 17 . 18 . 19 . 20 called, and
• - A directional control valve for controlling the Rekuperationsfunktion, hereinafter Rekuperationsventil 21 . 22 . 23 . 24 called.

To control the traversing cylinder is a 4/3-way valve, hereinafter central valve 28 called, provided. The two directional valves shown are as return valve 25 and return valve 26 designated.

The node 5 serves to recover the spring energy. For a better understanding, a cycle sequence will be described below. At the beginning of the cycle, the time after the molding removal is defined before closing the closing unit. All valve positions as in 3 are shown below as position 1 according to 4 designated. The other switching position is according to 4 referred to as position 2.

The 4/3 central valve 28 has three possible switching positions. Position 1 indicates the switching position required for extension (closing), position 0 the position for holding the position, position 2 denotes the switching position for retraction (opening).

To close the action valve 13 . 14 . 15 . 16 , the central valve 28 and the return valve 25 each in the passage / opening position (position 2).

The hydraulic accumulator 9 is discharged via interface A1, so that the traversing cylinder 27 extending. That is on the right side of the travel cylinder 27 located pressure fluid is caused by the travel movement of the Verfahrzylinders 27 ( 4a . 4b . 4c . 4d ) via interface A2 via the open return valve 25 in the tank 29 repressed.

To brake the movable plate 2 the closing unit becomes the return valve 25 switched to position 1. The displaced pressure medium can no longer be returned to the tank 29 but is forced into the recuperation line, which with the Rekuperationsventilen 21 . 22 . 23 . 24 connected is. About the recuperation valves 21 . 22 . 23 . 24 The displaced pressure medium can now optionally in one of the hydraulic accumulator 10 . 11 . 12 be pressed, depending on which Rekuperationsventil 22 . 23 . 24 is switched. Due to the back pressure in the store 10 . 11 . 12 becomes the movable plate 2 slowed down the closing unit.

At the same time, the selected hydraulic accumulator 10 . 11 . 12 charged by the displaced pressure medium to a certain extent. The switching times are selected by the control unit, not shown, so that the speed of the movable plate of the clamping unit is reduced shortly before positive locking to the desired level.

The choice of the hydraulic accumulator used for deceleration 9 . 10 . 11 . 12 depends on the cycle time and can vary. After the form-fitting of the two negative mold halves 1a and 1b switch the action valve 13 and the central valve 28 back to switching position 0. Subsequently, the clamping unit is closed by a lock (item 5, 1 and 2 ) mechanically locked.

When building up the closing force, the action valve switches 15 in the open position (position 2). The hydraulic accumulator 11 is discharged via interface A3 until a pressure equalization between the hydraulic accumulator 11 and the pressure pad 6 has set. The resulting closing force is dependent on the internal geometry of the pressure pad 6 and the dimensioning of the hydraulic accumulator 11 and can about the state of charge of the hydraulic accumulator 11 be varied. After the closing force has been built up, the action valve switches 15 in the closed position to hold the power.

After the closing force has been built up, the actual molding production takes place. The plasticized molding compound is passed through the plasticizing unit, not shown, in the mold cavity of negative mold halves 1a and 1b injected. After completion of mold filling, the holding pressure phase, which is taken over as the injection process of the screw of the plasticizing, to compensate for shrinkage and distortion. Subsequently, the screw rotation provides a defined amount of melt for the next cycle. Depending on the molding and material properties, the molded part remains in the cavity during the remaining cooling time until the demolding temperature is reached. All necessary associated axis movements are realized by external drives.

After the molded part has cooled to demolding, the closing force is first reduced. In order to make use of the energy contained in the elastically deformed closing unit and / or in the elastically deformed injection molding tool, according to the invention two embodiments can be carried out.

In the first embodiment, to reduce the closing force, the action valve 16 in switching position 1 connected. The pressure in the hydraulic accumulator 12 is at this time less than the pressure in the pressure pad 6 / 8th , The elastically deformed closing unit and the injection mold relax and displace the pressure medium contained in the pressure pad, until a pressure equilibrium between the pressure pad 6 / 8th and the memory 12 has set. Subsequently, action valve 16 back to switch position 0 and the return valve 26 in switching position 1 switched to the residual pressure in the pressure pad 6 / 8th dismantle. The so charged hydraulic accumulator 12 For example, it can be used to build up part of the closing force on the next cycle before the remaining pressure build-up required by the hydraulic accumulator 11 is realized.

In the second embodiment, the spring energy can be used to relieve the drive unit. For this purpose, the recuperation valve is released when the closing force is removed 30 connected at node K5. The force actuator A3 is connected directly to the suction side of the drive pump. By this measure, the pressure difference across the pump is lowered for a short period of time, whereby the required mechanical drive power and thus also reduces the electrical power required by the drive. It is advantageous over the first embodiment described above, that no delay times occur during the degradation of the closing force and the existing spring energy can theoretically be fully utilized.

The opening of the closing unit and the recovery of the kinetic energy by braking the movable plate proceed in an order corresponding to the closing operation, wherein when opening the tool, the action valve 14 is switched at node K2. The central valve 28 is switched to the extended position (position 2) at the beginning of the opening movement, and shortly before reaching the opening position of the closing unit, the movable plate is closed by closing the return valve 25 and diverting the pressure medium in the Rekuperationsleitung and the subsequent (counter) pressure build-up in one of the hydraulic accumulator 9 . 11 . 12 braked.

LIST OF REFERENCE NUMBERS

LIST OF REFERENCE NUMBERS

1

injection mold

1a

 Negative mold half

1b

 Negative mold half

2

Moving plate

3

Fixed plate

4

Hydraulic drive

4a

Verfahrzylinder

4b

Verfahrkolben

4c

Verfahrkolbenführung

4d

Pressure fluid chamber

5

 lock

6

 caul

7

differential cylinder

8th

Spring recoverable cylinder

9

hydraulic accumulator

10

hydraulic accumulator

11

hydraulic accumulator

12

hydraulic accumulator

13

action valve

14

action valve

15

action valve

16

action valve

17

charging valve

18

charging valve

19

charging valve

20

charging valve

21

Rekuperationsventil

22

 Rekuperationsventil

23

Rekuperationsventil

24

Rekuperationsventil

25

Return valve

26

Return valve

27

driving cylinder

28

central valve

29

Pump unit with reservoir

30

Rekuperationsventil

A1

interface

A2

interface

A3

interface

K1

junction

K2

junction

K3

junction

K4

junction

K5

junction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010049969 A1 [0005]

Cited non-patent literature

• Johannaber / Michaeli, "Handbook Injection Molding", Hanser 2001, pages 836-839 [0004]

Claims (14)

A method for energy recovery in a device for molding plastics, comprising a molding unit with a preferably stationary mold half and a movable mold half, which are coupled to form a forming cavity, and a hydraulic drive for the movable mold half and a molding material supply unit in the shaping In which the mechanical energy present in a shaping in the hydraulic system during the movement for closing and / or opening the shaping unit during the braking of the moving mold half, and / or relaxation of the closing force in the decoupling of the tool halves in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) is temporarily stored and the hydraulic drive for a molding operation can be fed. Method according to Claim 1, in which a hydraulic drive is used to move the movable mold half 4 with a travel cylinder ( 4a ) with by the Verfahrkolben ( 4b ) separate pressure medium spaces ( 4d ), wherein in the pressure medium space evacuating under pressure, a back pressure is built up to decelerate the movable mold half. Method according to one of claims 1 or 2, characterized in that the pressure medium chamber evacuating under pressure is hydraulically connected to at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) brings. Method according to one of the preceding claims, in which the mechanical energy released in a shaping operation during the relaxation of the closing force during the disengagement of the tool halves in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) is temporarily stored and the hydraulic drive for a molding operation can be fed. Method according to one of claims 1 to 4, characterized in that the at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) in a hydraulic connection with a hydraulic pump ( 29 ) to adjust the pressure in the hydraulic drive before, during or after molding. A method for energy recovery in a device for molding plastics, comprising a molding unit with a preferably stationary mold half and a movable mold half, which are coupled to form a forming cavity, and a hydraulic drive for the movable mold half and a molding material supply unit in the shaping A cavity according to any one of claims 1 to 5, comprising: - moving the at least one movable mold half by means of a positioning cylinder 7 from an open position to a closed position; - braking the movable mold half by pressurizing at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) and storage of the mechanical energy in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ); - Coupling of the tool halves and generating the closing pressure; - Production of a molding; - Relaxing of the tool halves under pressure of a hydraulic accumulator ( 9 . 10 . 11 . 12 ) and storing the mechanical energy in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) - Moving the at least one movable mold half by means of a positioning cylinder 7 from the closed position to the open position, and optionally, - braking the movable mold half by pressurizing at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) and storage of the mechanical energy in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ); Setting a desired pressure in the at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) by means of a hydraulic pump 29 , A method according to claim 6, wherein in addition to the process of the at least one movable mold half in the open position and before setting the target pressure, the movable mold half is pressurized by pressurizing at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) is braked and the mechanical energy in at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) is stored. An apparatus for molding plastics, comprising a forming unit with a stationary mold half and a movable mold half, which can be coupled to form a shaping cavity, and a hydraulic drive 4 with a travel cylinder ( 4a ) with by the Verfahrkolben ( 4b ) separate pressure medium spaces ( 4d ) for which the movable mold half and a molding compound supply unit in the shaping cavity, characterized in that at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ), this hydraulic accumulator ( 9 . 10 . 11 . 12 ) via at least one valve ( 13 . 14 . 15 . 16 ) is hydraulically connected to at least one pressure medium space. Apparatus according to claim 8, characterized in that the at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) via a pump valve ( 17 . 18 . 19 . 20 ), preferably a 2/2-way valve is connected to at least one pump unit, via which the hydraulic accumulator ( 9 . 10 . 11 . 12 ) can be acted upon with pressure. Device according to one of claims 8 or 9, characterized in that the pump unit has a reservoir, which is filled with a pressure-transmitting medium, and / or that at least one pressure element is connected via a circulation valve with an inlet of a reservoir. Device according to one of claims 8 to 10, characterized in that the pressure element via a recuperation ( 21 . 22 . 23 . 24 ) with at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ), and / or that the pressure element, preferably a displacement cylinder ( 4a ), via a central valve ( 28 ) and the at least one valve ( 13 . 14 . 15 . 16 ) with the hydraulic accumulator ( 9 . 10 . 11 . 12 ), and / or that the recuperation valves ( 21 . 22 . 23 . 24 ) are interconnected. Device according to one of claims 8 to 11, characterized in that the device comprises a hydraulic drive and at least two hydraulic accumulators ( 9 . 10 . 11 . 12 ), which alternately a Verfahrzylinder ( 4a ) for opening and closing a stationary mold half with pressure, and when braking the stationary mold half by pressurizing another hydraulic accumulator ( 9 . 10 . 11 . 12 ) temporarily store the mechanical energy and at least one hydraulic accumulator ( 9 . 10 . 11 . 12 ) for pressurizing a pressure pad ( 6 ) and for establishing a closing pressure is provided and at least one further hydraulic accumulator ( 9 . 10 . 11 . 12 ) for temporary storage of the released mechanical energy during the relaxation of the pressure pad ( 6 ) is provided. Closing unit for an injection molding machine, in particular a 2-plate closing unit for an injection molding machine, comprising a fixed plate, a movable plate, at least one drive for moving the movable plate via a travel path when closing and when driving the closing unit, with at least one in a guide stored Verfahrkolbenstange, which is connected to a Verfahrkolben in the displacement cylinder on the fixed plate, and wherein the guide of the Verfahrkolbenstange on the movable plate is associated with a respective locking device, the locking elements with the associated guide is engageable to form a locked state, The movement cylinder is designed for moving the movable plate over a section of the travel path of the movable plate, - Both sides of the Verfahrkolbens in the Verfahrzylinder be acted upon with a pressure medium, so that the Verfahrkolben is movable within the Verfahrzylinders and relative to this and the fixed plate both in the closing direction and in the opening direction over a portion of the travel path with the Verfahrkolbenstange and the movable plate . - Each pressure fluid chamber in the displacement cylinder is associated with at least one hydraulic accumulator, which communicates with the pressure medium space in valve-controlled hydraulic connection, and - A control unit for operating the hydraulic actuators and valves is provided. Device according to claim 13, which additionally or alternatively to the hydraulic accumulator, which is in valve-controlled hydraulic connection with the pressure medium space in the displacement cylinder, at least one hydraulic accumulator, which communicates with the pressure medium space in the pressure pad 6 in valve-controlled hydraulic connection stands.

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