CN113000816A

CN113000816A - Hydraulic casting unit

Info

Publication number: CN113000816A
Application number: CN202011504604.1A
Authority: CN
Inventors: D-W·赫罗尔德; H·恩格特
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-12-19
Filing date: 2020-12-18
Publication date: 2021-06-22
Also published as: DE102019220133A1

Abstract

The invention relates to a casting unit, the casting cylinder of which can be operated regeneratively in the pre-charging phase by means of a flow control valve. Via this flow control valve, a booster unit, for example a pressure booster or a high-pressure accumulator, is also connected in the pressure holding phase.

Description

Hydraulic casting unit

Technical Field

The invention relates to a hydraulic casting unit according to the preamble of claim 1.

Background

The basic structure of such a casting unit for use in a prototype such as an injection molding machine, a die-casting molding machine or a thixomolding machine is disclosed, for example, in document DE 102017220832 a1, which originates from the applicant. Accordingly, the casting unit has a double-acting casting cylinder, the piston of which defines a bottom space on the piston bottom side and the end face of which on the piston rod side defines an annular chamber. In the known solution, the bottom space is connected to the low-pressure reservoir in the pre-filling phase and the mold filling phase by means of, for example, an 2/2 reversing seat valve, which is embodied as an active logic, wherein the annular chamber of the casting cylinder is connected to the bottom space by means of a control valve, so that the pressure medium which is displaced from the smaller annular chamber in the pre-filling phase is supplied to the larger bottom space by means of the control valve in the regeneration line. In the mold filling phase, a pressure medium connection to the magazine can be opened for injection by means of a control valve on the magazine side and the control valve is closed between the piston chamber and the ring chamber. In the pressure holding phase, the bottom space is then connected to the high-pressure reservoir via a further regulating valve, wherein the pressure medium connection to the low-pressure reservoir is blocked by active logic. During this holding pressure phase, the aforementioned regulating valve on the feed tank side keeps open the pressure medium connection between the annular chamber and the feed tank, so that the melt in the mold cavity is compressed with high pressure and possible material losses are compensated.

The basic structure of the active logic used in this cast cell is known from document DE 102005035170B 4.

In a casting cell of the type disclosed in DE 102017221500 a1, no regeneration circuit is provided. In the pre-charging and mold-charging phases, the bottom space is charged by active logic with a low-pressure accumulator and the control valve on the outlet side is switched on, so that the piston of the casting cylinder is moved out at a predetermined speed. During the transition from the pre-charging phase to the mold charging phase, the valve on this outlet side is continuously switched on, so that the piston accelerates and moves out at a higher speed. The pressure medium emerging from the reduced annular chamber flows through the outlet-side control valve to the outlet reservoir and then flows out to the tank through the non-return valve or the flap when a predetermined pressure is reached in the outlet reservoir. This reduces the maximum volume flow to the tank and the resulting turbulence.

After the end of the pre-charging phase, the pressure booster (multiplier cylinder) is accelerated in order to introduce the dwell phase, and a higher pressure builds up in the bottom space. In this case, the acceleration of the pressure booster is achieved by connecting the annular chamber of the pressure booster via a control valve to a low-pressure accumulator or a tank.

Disclosure of Invention

The object of the present invention is therefore to create a casting unit which allows an optimized casting process with low outlay on equipment technology.

This object is achieved by a casting unit having the features of claim 1.

Advantageous embodiments of the invention are the subject matter of the dependent claims.

The hydraulic casting unit according to the invention, which is preferably designed for use in an injection molding machine, a diecasting machine or a thixomolding machine, has a casting cylinder designed as a differential cylinder, the piston of which defines a bottom space on the bottom side and an annular chamber on the piston rod side. The casting unit furthermore has a control valve which is designed to connect the annular chamber to the bottom space in the manner of a regeneration line during the pre-charging and/or mold-charging phase. The casting unit furthermore has an outlet valve for connecting a tank line connected to the annular chamber to the tank during the mold filling phase and the pressure holding phase. According to the invention, a low-pressure source which can be connected to the bottom space via a shut-off valve device (low-pressure valve) and a hydraulic pressure intensifier unit are provided, which is designed to support the removal movement of the casting cylinder during the pressure holding phase. According to the invention, the control valve is designed as a multi-way flow control valve, which is referred to below as a flow control valve, with a closed position, wherein the slide of the flow control valve is designed to open a pressure medium connection between the bottom space and the annular chamber in a first control direction in the manner of the aforementioned regeneration line and to activate the booster unit in a second control direction. The pressure medium can preferably also be discharged from the bottom space at the time of pressure regulation by means of a flow regulating valve.

In this circuit, only two control valves (the flow control valve described above and the flow control valve in the outlet) are required for the basic functions (the pre-charging phase is regenerative, the mold charging phase and the holding pressure phase), so that the technical outlay on the device is significantly reduced compared to conventional solutions. The flow control valve which enables the regenerative operation of the casting cylinder allows the use of a smaller accumulator, wherein fewer cavitation and less wear occur in the regeneration function by the flow control valve on the basis of a smaller pressure difference, and the operation of the casting cylinder is performed at a lower speed with greater accuracy.

The pressure build-up and pressure reduction in the pressure holding phase is essentially effected by the flow control valve and the intensifier unit, so that a significant system improvement is created by the design according to the invention.

In one embodiment of the invention, the reinforcing unit is formed by a high-pressure accumulator which is connected to the bottom space in the second adjustment direction via a flow control valve, so that the piston of the casting cylinder is subjected to a high pressure in the removal direction. The second adjustment direction enables a regeneration circuit and a pressure reduction in the pressure holding regulation.

In an alternative solution, the booster unit is designed as a pressure booster (multiplier), whose booster piston delimits a booster annular chamber and a booster pressure chamber, which can be connected for acceleration to a low-pressure reservoir via a shut-off valve or the like. The flow control valve can thereby connect the pressure medium connection of the pressure booster annular chamber to the tank line in the second adjustment direction.

The flow control valve can be designed, for example, as a three-way reversing flow control valve which is controlled electrohydraulic.

In one variant of the invention, the shut-off valve device is designed as 2/2-reversing active logic with an auxiliary valve. The active logic makes it possible to close or open the pressure medium connection between the low-pressure accumulator and the bottom space of the casting cylinder and to close it very quickly in phase III when the pressure builds up, so that the mold charging phase can be ended very quickly and accurately.

In an alternative solution, the shut-off valve device is instead of being designed with an active logic shut-off valve arranged downstream of the low-pressure source, wherein a check valve is arranged between this shut-off valve and the bottom space of the casting cylinder. The shut-off valve closes and opens the connection to the casting cylinder. A check valve closes the connection when pressure builds in phase III.

According to an advantageous further development of the invention, the pressure in the bottom space can be reduced by the switching valve toward the tank T.

The outlet valve can be designed as a two-way flow control valve which is pre-controlled by electro-hydraulic pressure. The outlet control can also be carried out by other components, for example by means of a valve which can be adjusted by means of a servomotor.

For the purpose of pre-tensioning and for loading the low-pressure accumulator and/or the high-pressure accumulator, the casting unit according to the invention is designed with a hydraulic pump which can be designed as a control pump or as a fixed displacement pump with a servomotor and a servo converter or as a control pump with a three-phase electric motor and a frequency converter or as a control pump with a three-phase electric motor.

In order to avoid the starting pressure when the preliminary charging phase is initiated, the casting unit according to the invention can also be designed with devices for pretensioning the piston side and the ring side of the casting cylinder and/or the pressure booster. The gentle feed movement can also be controlled by a continuous valve or a shut-off valve on the inlet side and a flap downstream of the shut-off valve or by a pump.

For this purpose, for example, a back pressure valve can be used, by means of which the pressure connection of the pump can be connected to the annular chamber of the casting cylinder or of the pressure booster for pretensioning. The pretensioning can also be accomplished by just appropriately controlling the pump. This actuation can also be used to load the memory.

In one embodiment of the invention, the pressure chamber on the bottom side of the pressure booster is connected directly to the tank or to the pressure connection of the pump via two switching valves, which are embodied, for example, as seat valves.

Preferred embodiments of the invention are explained in more detail below with the aid of schematic drawings.

Drawings

FIG. 1 is a schematic view of a casting unit;

FIG. 2 is a simplified hydraulic circuit diagram of the first embodiment;

FIG. 3 is a hydraulic circuit diagram according to a variant of the embodiment of FIG. 2; and is

Fig. 4 is a hydraulic circuit diagram according to a further variant of the exemplary embodiment of fig. 2.

Detailed Description

Fig. 1 shows the essential mechanical components of a hydraulic casting unit 1 according to the invention of a die casting machine.

The casting unit 1 has a casting cylinder 10, which is designed as a differential cylinder and whose piston 11 is designed correspondingly with a piston rod 12. The piston 11 and the housing 13 of the casting cylinder together define a bottom space 14 on the bottom side and an annular chamber 15 through which the piston rod 12 extends. At the end section of the piston rod 12 projecting from the housing 13, a cast piston 16 is fixed, which is inserted into a shot chamber 18 of a cast bush 17. In this injection chamber, a filling opening 19 for a liquid or pasty molding material, referred to below as melt, is located from which the workpiece to be molded is to be produced. The casting liner 17 is attached to a pattern 20, which is typically made up of movable and stationary pattern halves. The two mould halves define a mould cavity 21, also called mould cavity, which is designed to correspond to the geometry of the workpiece to be formed. The shot chamber 18 opens into the mold cavity 21 through a casting channel 22.

Such a casting unit 1 serves for introducing a melt into a mold 20, wherein, due to the rapid solidification process, a high speed and subsequently a high pressure are required for the charging to completely fill the mold 20 and to compress and to compensate for the shrinkage of the material during solidification.

In the exemplary embodiment according to the invention shown in fig. 2, a pressure booster 24, also referred to as a multiplier, which is designed, for example, as a differential cylinder, is assigned to the casting cylinder 10 as a booster unit. The primary piston 26 defines a booster pressure chamber 28 with a bottom surface and a piston rod 30 extends through a booster annular chamber 32. The construction of such a supercharger 24 is known and therefore further explanation is not necessary.

The pressure medium supply of the illustrated casting unit 1 takes place via a hydraulic pump 34, which in the illustrated embodiment is designed as a fixed displacement pump and is driven by a speed-regulated electric motor 36, which is designed, for example, as a servomotor with a servo converter or as a three-phase motor with a frequency converter. The pressure connection of the hydraulic pump is connected to the bottom space 14 via a pump line 40 and a shut-off valve 42 arranged in the pump line and designed as an 2/2 directional valve. In its illustrated spring-biased basic position, the shut-off valve 42 interrupts the pressure medium connection between the hydraulic pump 34 and the bottom space 14 and can be moved into the passage position by means of a switching magnet.

The annular chamber 15 of the casting cylinder 10 is connected to the head box T via a line 44, wherein an outlet valve 46 is arranged in this line. In the exemplary embodiment shown, this outlet valve is designed as an electrohydraulic pilot-controlled 2/2 flow control valve, which in its basic position blocks the pressure medium connection to the tank T and, by pilot control of the drive control electrohydraulic pressure, switches on the opening cross section to the tank T as a function of the control signal.

The line 44 and the pump line 40 are connected by a shut-off valve 48 designed as an 2/2 reversing valve, which is arranged in the pretension line 50. This pretensioning line is blocked in the spring-pretensioned base position of the back pressure valve 48 and can be switched on by a switching magnet that actuates the blocking valve 48. The casting cylinder 10 can also be moved back by appropriate actuation of the valve 48.

The pressure at the outlet of the hydraulic pump 34 is limited in a manner known per se by a pressure limiting valve 52 which opens towards the tank T.

According to the invention, a flow control valve 54, which in the exemplary embodiment shown is designed as a continuously adjustable, electrohydraulic pilot-controlled installation control valve (three-way flow control valve) with three connections, is associated with the pressure booster 24 and the casting cylinder 10. This flow regulating valve has a connection 1, a connection 2 and a connection 3.

The flow control valve 54 has a position in which the pressure medium connection between the

connections

1, 2 and 3 is closed. By means of a corresponding actuation, the control slide of the flow control valve 54 can be adjusted in the sense that the pressure medium connection between the connection 1 and the connection 3 is established. In the corresponding control, the pressure medium connection from the connection 2 to the connection 3 is switched on (see fig. 2).

The connection 2 is connected in the illustrated embodiment to the booster annular chamber 32 via a line 56. The pressure line 58 leads into a line section 41 running downstream of the shut-off valve 42, and the pressure line leads to a connection B of a pilot-controlled 2/2 reversing seat valve designed as an active logic 60. The pilot control is performed by an auxiliary valve 62 designed as an 4/2 directional valve. The input terminal connector a of the active logic 60 is connected to a low pressure reservoir 66 by a low pressure reservoir line 64. The active logic 60 may also be installed in reverse in view of the tap A, B.

One possible structure of the active logic 60 is known from the documents DE 102017220832 a1 and DE 102005035170B 4 cited in the introduction to the description, so that only the structural elements important for understanding the invention are explained here and the rest of the description refers to this prior art. Accordingly, the active logic 60 has a stepped master piston 70, which is pretensioned against the valve seat 68 with the pressure from the low-pressure reservoir ND against the surface a5 and blocks the pressure medium connection between the connection A, B and thus between the low-pressure reservoir line 64 and the pressure line 58. The active logic 60 can also be designed, for example, with two control surfaces and a pressure equalization as well as with a switching auxiliary valve (see DE 102017220832 a1 and patent DE 102005035170B 4).

The tank line 84 is connected to the tank connection of the auxiliary valve 62 and the input connection of the auxiliary valve 62 is connected via a line 88 to a pressure reservoir 90 which is pressurized to a higher pressure than the low pressure reservoir 66. By energizing the switching magnet of the auxiliary valve 62, this auxiliary valve can be adjusted against the force of a spring into a switching position in which the annular control chamber of the active logic 60 is connected to the reservoir 90, so that, on account of the higher pressure in the reservoir 90 acting on the annular end face a4, the main piston 70 is lifted from the valve seat 68 and the fluid connection between the connections A, B is established. In the above-described alternative embodiment of the active logic 60 with two control surfaces, it is not necessarily necessary to provide a higher control pressure.

Alternatively, it is also possible to design the annular end face a4 which delimits the annular control chamber with a larger effective surface than the difference in area a5-A3, which in this case is sufficient to connect the annular control chamber to the low-pressure accumulator 66 in the switching position of the auxiliary valve 62 (see fig. 3), since the force effective in the opening direction, which is essentially caused by the large annular end face a4 and the face A3, is greater than the force effective in the closing direction, which is determined by the force of the spring force and the pressure acting on the face a 5.

The active logic 60 is designed in such a way that it can be closed very reproducibly with minimal pressure loss and minimal switching time when actuated correspondingly by the auxiliary valve 62. The stroke of the active logic 60 may also be limited in order to optimize the later closing characteristic. With this special structural design of the active logic 60, only a small control oil flow is required even at large nominal sizes in order to open and close the active logic 60 quickly and reproducibly.

Furthermore, the operational safety is increased by actively opening and closing the active logic 60 by means of the auxiliary valve 62 and by safely keeping the active logic 60 closed by means of the reservoir pressure. It is possible here to select the conditions for the shutdown by actively shutting down the active logic 60. This closing can be effected, for example, as a function of pressure, load force, operating stroke, operating speed, etc.

As shown in fig. 2, the low-pressure accumulator line 64 can be connected in a manner known per se to the pressure booster chamber 28 via an 2/2 switching valve, which is referred to below as an accumulator shut-off valve 92.

A pressure relief line 94 branches off from the pressure line 58, in which a pressure relief valve 96 is provided. This pressure relief valve is designed as an 2/2 reversing valve and in the illustrated spring-biased basic position blocks the pressure relief line 94 to the tank T. By energizing the switching magnet, the pressure relief valve 96 can be brought into a passage position in which a fluid connection to the tank T is established.

The operation of the casting unit 1 shown in fig. 2 during the initially described phase is explained next.

In order to prevent the opening of the active logic 60, which is also referred to as an accumulator shut-off valve, during the priming phase of the casting cylinder 10 from generating a pressure wave in the direction of the casting cylinder 10, which generates the priming pressure, the casting cylinder 10 is pretensioned before the priming phase is initiated. This is achieved in that, in the casting cylinder 10 and the pressure booster 24 which are moved back (after the last shot), the annular chamber 15 and the pressure booster annular chamber 32 of the casting cylinder 10 can be pretensioned to a maximum pump pressure by means of the hydraulic pump 34 and the back pressure valve 48 which is pivoted into its open position and the flow control valve 54 which is adjusted by means of electrohydraulic pre-control in the direction of the position shown in fig. 2 in which the fluid connection between the connection 3 and the connection 2 is opened. The shut-off valve 42 and the back-pressure valve 48 are preferably designed with a non-return function.

In the next step, the melt is introduced into the shot chamber 18 of the casting sleeve 17 through the filling opening 19 and is introduced into the pre-filling phase. For this purpose, the hydraulic pump 34 is controlled via a ramp function and pressurizes the bottom space 14 of the casting cylinder 10 to the reservoir pressure via a valve 42. The casting cylinder 10 is thus moved out a little bit slowly and without a starting pressure counter to the pretension until the fluid contained in the annular chamber 15 is compressed and thus there is a force equalization. It is important here that a smooth pressure equalization between the low-pressure accumulator 66 and the bottom space 14 of the casting cylinder 10 is achieved by this control. The low-pressure accumulator 66 can then be connected to the bottom space 14 via the active logic 60 (accumulator shut-off valve) and the low-pressure accumulator 66 can be connected to the pressure booster pressure chamber 28 via the low-pressure shut-off valve 92.

This approach is not necessary provided that pump 34 can generate a sufficiently high pressure. In the correspondingly highly pretensioned annular chamber 15, the low-pressure accumulator 66 can also be connected to the piston chamber 14 via the active logic 60.

The flow control valve 54 is then adjusted by way of pilot control in the direction in which the two

connections

1 and 3 are connected, so that the pressure medium emerging from the annular chamber 15 is fed directly to the bottom space 14 in the form of a regeneration line. This allows the casting cylinder 10 to start and move gently (smoothly, regeneratively, and regulated). The melt is thereby accelerated and moved in the direction of the mold cavity 21. This is carried out until the melt reaches the mould section.

By means of the regenerative operation of the casting cylinder 10 in the pre-charging phase, little pressure medium is taken out of the low-pressure accumulator 66, so that this low-pressure accumulator can be designed with a smaller volume than in conventional solutions. Furthermore, by a smaller pressure drop at the flow regulating valve 54, a better resolution of the casting cylinder speed is achieved, so that the casting cylinder 10 can be operated at a smaller speed.

A further advantage of the regeneration operation is that, due to the low pressure loss at the flow control valve 54 and due to the fact that the pressure medium flows out of the annular chamber 15 not against the tank pressure (0 bar) but rather against the pressure in the low-pressure accumulator 66, cavitation and therefore wear occur very little at the piston 11 and at the housing 13 of the casting cylinder and at the associated control block.

Furthermore, the pressure in the bottom space 14 can be actively influenced in the sense of a reduced pressure by appropriately controlling the flow regulating valve 54.

As soon as the melt reaches the mold cross section, the actual mold charging process (phase II) is initiated. With mold charging (injection) at lower mold charging forces, the operation is also regenerative. Correspondingly, at the point in time when the melt reaches the mold cross section, the flow control valve 54 is adjusted, for example, with a jump function into a position in which the pressure medium connection between the annular chamber 14 and the bottom space 15 is opened further, so that the melt is injected into the mold 20 at a high injection speed (up to 10 m/s). In this case, the pressure medium is also regeneratively operated, i.e. the pressure medium emerging from the annular chamber 15 is supplied to the enlarged bottom space 14.

The advantage of this is that less pressure medium must be removed from the low-pressure reservoir 66 in phase II than is the case in conventional solutions.

In the case of injection at high mold loading forces, at the point in time when the melt reaches the mold cross section, the flow control valve 54 is moved into its closed position, for example, with a jump function, so that the pressure medium connection between the annular chamber 15 and the bottom space 14 is interrupted. In parallel, the flow control valve 46 in the outlet opens, for example with a jump function, according to a predetermined opening cross section towards the tank T. This results in the melt being injected into the mold cavity 21 at a high injection speed, wherein the difference from the low mold charge pressure is that it is not operated regeneratively and therefore the maximum force of the casting cylinder 10 can be used.

In principle, a hybrid model is also conceivable, in which the flow control valve 54 is adjusted into its blocking position only during the first phase II as a function of the load force.

Stage II can also be run completely regeneratively. However, this presupposes that the required load force in phase II can also be achieved in the regeneration line. In this case, the flow control valve 46 can be replaced by a rapidly switchable valve for pressure relief of the annular chamber 15 in phase III.

After the mold cavity 21 has been completely filled, a transition is made to phase III. For this purpose, at the end of the mold filling, the flow control valve 54 is connected by pilot control in the direction of opening from 3 to 2, so that the pressure booster annular chamber 32 is connected to the line 44 via the flow control valve 54. In parallel with the adjustment of the flow control valve 54, the flow control valve 46 is switched on toward the feed tank T, so that the primary piston 26 is accelerated by the pressure relief of the pressure booster ring chamber 32 and correspondingly a high pressure builds up in the bottom space 14, so that the piston 11 is acted upon with high pressure and the melt is recompressed. After the desired dwell pressure is reached, the flow regulating valve 54 is again reset back to the closed position by the pressure regulator. Without closing the flow control valve 54 fast enough, it is possible to reduce the pressure overshoot by switching on the connection from 1 to 3.

Accordingly, the flow control valve 54 has a dual function, i.e. it controls the regenerative connection of the annular chamber 15 and the bottom space 14 on the one hand and on the other hand introduces an acceleration of the pressure booster 24 (multiplier). This dual effect makes it possible to dispense with a control valve in comparison with the solution described at the outset.

Fig. 3 shows a hydraulic circuit diagram of a variant of the casting unit 1 according to fig. 2. The difference is that in the exemplary embodiment according to fig. 3, the boost unit is not formed by the pressure booster 24, but by a high-pressure accumulator 98, which can be switched on by a high-pressure accumulator valve 100. In the exemplary embodiment according to fig. 3, the flow control valve 54 is also adjusted by its pre-control via the electrohydraulic pressure counter to the force of a spring into the position shown, in which the fluid connection between the

connections

1 and 3 is opened, so that the annular chamber 15 is connected to the bottom space 14 and the casting cylinder 10 can be operated regeneratively. The connection between the

connections

1 and 2 can be established by means of the flow control valve 54, a high-pressure accumulator line 102 being connected to the latter, in which a high-pressure accumulator valve 100 is arranged.

In the exemplary embodiment according to fig. 3, the hydraulic pump 34 is also designed as a displacement pump, for example, in the form of a shaft-piston arrangement. Correspondingly, the electric motor 36 is designed as a metering motor. Of course, a fixed displacement pump with the drive variant explained with reference to fig. 2 is also used in the circuit according to fig. 3.

The exemplary embodiment according to fig. 3 also substantially corresponds to the exemplary embodiment according to fig. 2, so that reference can be made to the above statements as to the function and structure of the remaining components.

Before the phase I is initiated, the pressure medium connection between the connection 2 of the flow control valve 54 and the high-pressure accumulator 98 can be opened via the high-pressure accumulator valve 100, but this high pressure does not act in the bottom space 14, so that the connection 2 is blocked. This bottom space 14 is connected to the annular chamber 15 via the flow control valve 54 as explained above, so that the regeneration operation of the casting cylinder 10 is completed. The control during the stages I and II of the casting process is similar to the description of the mode of operation of the casting unit 1 according to fig. 2.

To transition to phase III, high-voltage accumulator 98 is then switched on. This is achieved by adjusting the flow control valve 54 in the direction in which the direct connection between the annular chamber 15 and the bottom space 14 is broken and the fluid connection between the connection 2 and the connection 1 is closed, so that correspondingly in the bottom space 14, a high pressure is available. At the same time, the flow control valve 46 in the outlet is opened, so that the pressure medium emerging from the annular chamber 15 can flow out to the tank T. The use of the high-pressure accumulator 98 eliminates the costly acceleration of the conventional pressure booster 24 in phase III, so that only little pressure medium and therefore only little energy is required for the acceleration. The flow control valve 54 in the inlet to the casting cylinder 10 must not be opened until the required pressure is built up from 1 to 2. Since the moving mass of the pressure booster 24 must be eliminated and therefore also not braked, the pressure build-up can be carried out more dynamically than in the exemplary embodiment according to fig. 2. The quality of the adjustment is also improved. Another advantage is that the additional dead volume for inserting the piston rod 30 of the pressure booster 24 is eliminated on the casting cylinder side and the pressure medium required for actuating the pressure booster 24 on the basis of the area of the pressure booster is not required. The pressure build-up can thus be done much faster with the same volume flow in the inlet. Furthermore, this allows the use of a flow regulating valve 54 designed with smaller nominal dimensions. Loading the high-pressure accumulator 98 may be accomplished, for example, by a high-pressure pump or booster.

The applicant reserves the right to apply his own independent claim directly to the high-pressure accumulator 98 to establish the pressure required for compression at the casting cylinder 10.

Fig. 4 shows a variant of the exemplary embodiment according to fig. 2, in which the bottom-side pressure booster chamber 28 can be connected to the pump line 40 via a switching valve 104 and to the tank T via a further switching valve 106. In the basic position shown, the two switching

valves

104, 106 are pretensioned into their blocking position and can each be moved into the open position by energizing the switching magnets, so that the pressure booster pressure chamber 28 is either charged with the pressure at the output of the pump 34 (switching on the switching valve 104) or is relieved of pressure towards the tank T (switching valve 106 in the open position).

The embodiment according to fig. 4 corresponds to the embodiment explained with reference to fig. 2, and therefore no further explanation is necessary.

The described casting unit has the advantage over conventional solutions that the pressure medium emerging from the annular chamber 15 can be supplied directly to the bottom space 14 of the casting cylinder 10 via the flow control valve 54 by regenerative operation of the casting cylinder 10. The pressure build-up and pressure reduction in phase III can also be controlled by this flow control valve 54. Another particularity is that the active logic 60 is actively turned off at the end of phase II.

The active logic may also be replaced by a shut-off valve and an external check valve.

A casting unit is disclosed, the casting cylinder of which can be operated regeneratively by means of a flow control valve in a pre-charging phase. Via this flow control valve, an intensifier unit, for example a pressure booster or a high-pressure accumulator, is also connected in the pressure holding phase.

List of reference numerals

1 casting unit

10 casting cylinder

11 piston

12 piston rod

13 casing

14 bottom space

15 toroidal chamber

16 casting piston

17 casting liner

18 injection chamber

19 charging opening

20 model

21 model cavity

22 casting channel

24 supercharger/multiplier

26 Primary piston

28 pressure chamber of supercharger

30 piston rod

32 supercharger annular chamber

34 Hydraulic pump

36 motor

40 pump line

41 line section

42 stop valve

44 pipeline

46 flow control valve (outlet valve)

48 back pressure valve

50 Pre-tensioned pipeline

52 pressure limiting valve

54 flow regulating valve

56 connecting line

58 pressure line

60 active logic

62 auxiliary valve

64 Low pressure memory line

66 low voltage storage

68 valve seat

70 primary piston

84 bin line

88 pipeline

90 memory

92 storage cut-off valve

94 pressure relief pipeline

96 pressure relief valve

98 high-voltage storage

100 high pressure accumulator valve

102 high pressure accumulator line

104 switching valve

106 additional on-off valve

Claims

1. Hydraulic casting unit of a prototype, in particular of an injection molding machine, a die-casting machine or a thixoforming machine, with: a casting cylinder (10) designed as a differential cylinder, the piston (11) of which defines a bottom space (14) on the bottom side and an annular chamber (15) on the piston rod side; a regulating valve designed to connect the annular chamber (15) with the bottom space (14); and a regulating valve for connecting a line (44) connected to the annular chamber (15) to the tank (T); and a low pressure source connectable to the bottom space (14) via a shut-off valve arrangement; and a hydraulic intensifying unit designed to support the removal movement of the casting cylinder (10) during the dwell phase, characterized in that the regulating valve is designed as a flow regulating valve (54), the slide valve of which opens the pressure medium connection between the bottom space (14) and the annular chamber (15) in one adjusting direction and activates the intensifying unit in the other adjusting direction.

2. Casting unit according to claim 1, wherein the reinforcement unit is a high-pressure accumulator (98) which is connected to the bottom space (14) in the other adjustment direction by the flow control valve (54).

3. Casting unit according to claim 1, wherein the booster unit is a booster (24) whose primary piston (26) delimits with a smaller end face a booster annular chamber (32) and with a larger end face a booster pressure chamber (28) which can be connected to a low-pressure source via a reservoir shut-off valve (92), wherein the pressure medium connection of the booster annular chamber (32) to the line (44) can be connected in the further adjustment direction via the flow control valve (54).

4. Casting unit according to any of the preceding claims, wherein the flow control valve (54) is designed as a three-way flow control valve which is preferably electrohydraulic pre-tensioned.

5. Casting unit according to any of the preceding claims, wherein the shut-off valve arrangement is designed as an 2/2-reversing active logic (60) with an auxiliary valve (62).

6. Casting unit according to any one of claims 1 to 4, wherein the shut-off valve arrangement is designed as a valve arrangement with a shut-off valve assigned to a low pressure source and a non-return valve arranged between the shut-off valve and the bottom space (14) of the casting cylinder (10).

7. Casting unit according to any one of the preceding claims, with a switching valve (92) for connecting the output of the shut-off valve arrangement, in particular the reversing active logic (60), and the pressure medium flow path between the bottom space (14) of the casting cylinder (10) and the tank (T).

8. Casting unit according to any one of the preceding claims, wherein the outlet valve (46) is designed as a two-way flow regulating valve which is pre-controlled electro-hydraulically.

9. Casting unit according to one of the preceding claims, with a hydraulic pump (34), wherein the hydraulic pump is designed as a booster pump or as a fixed displacement pump with a servomotor and a servo converter or as a booster pump with a three-phase motor and a frequency converter or as a booster pump with a three-phase motor.

10. Casting unit according to any of the preceding claims, with means for pre-tensioning the casting cylinder (10) and/or the pressure booster (24).

11. Casting unit according to claim 9, with a shut-off valve (48) which is designed to connect a pressure connection of the hydraulic pump (34) to the booster annular chamber (32) and/or to the annular chamber (15) of the casting cylinder (10) via the flow control valve (54).