Hydraulic casting unit

Abstract

The present invention discloses a casting unit having a casting cylinder configured as a differential cylinder and a hydraulic booster.

Description

[Technical Field]

[0001] This invention relates to a hydraulic casting unit according to the foregoing of technical solution 1 of the present invention. [Previous Technology]

[0002] For example, disclosure DE 10 2017 220 836 A1, derived from the applicant, discloses the basic construction of a casting unit of this type used in molding machines such as injection molding machines, die casting machines, or thixomolding machines. Thus, the casting unit has a double-acting casting cylinder, the piston of which defines a base chamber proximal to the piston base, and the piston rod proximal end face of which defines an annular chamber. In known solutions, during the pre-filling and mold filling stages, the base chamber is connected to a low-pressure reservoir, for example, via a 2 / 2-way seat valve configured as an active logic system, wherein the annular chamber of the casting cylinder is connected to the base chamber via a control valve, such that pressurized medium displaced from the decreasing annular chamber during the pre-filling stage is supplied to the increasing base chamber via the control valve in a differential or regeneration circuit. During the mold filling stage, the connection to the pressurized medium in the injection reservoir is actuated by a control valve near the reservoir, and the control valve between the piston chamber and the annular chamber can be closed. Then, during the holding stage, the base chamber is connected to the high-pressure reservoir by another control valve, where an active logic system blocks the connection to the low-pressure reservoir. During this holding stage, the pressurized medium connection between the annular chamber and the reservoir is kept open by the previously mentioned reservoir proximal control valve, allowing the melt in the chamber to be compressed under high pressure and compensating for any potential material shrinkage.

[0003] The basic structure of the active logic system used in this casting unit is known from the publicly disclosed case DE 10 2005 035 170 B4.

[0004] The casting unit disclosed in Publication DE 10 2017 221 500 A1 does not include any differential or regeneration circuits. During the pre-filling and mold filling stages, the base chamber of the active logic system is pressure-impacted by the low-pressure chamber, and the outflow proximal control valve is actuated, causing the piston of the casting cylinder to expand at a predetermined speed. During the transition from the pre-filling stage to the mold filling stage, this outflow proximal valve is further actuated, causing the piston to accelerate and expand at a relatively high speed. The pressurized medium displaced from the decreasing annular chamber flows to the outflow reservoir via the outflow proximal control valve, and when the predetermined pressure is reached in the outflow reservoir, it flows towards the reservoir via a check valve or orifice. Thus, the maximum volumetric flow rate to the reservoir and the associated turbulence are reduced. After the pre-filling stage ends, the pressure booster (multiplier cylinder) is accelerated to initiate the holding stage, and the increased pressure accumulates in the base chamber described herein. In this paper, the acceleration of the pressure booster is achieved because the annular chamber of the pressure booster is connected to the low-pressure reservoir or tank via a control valve. [Summary of the Invention]

[0005] In contrast, the present invention is based on the purpose of realizing a casting unit with a differential circuit and a pressure enhancer, which can realize an optimized casting process with lower equipment complexity.

[0006] This objective is achieved by a casting unit having the features of patented technology solution 1.

[0007] An advantageous improvement of the present invention is the subject matter of a dependent technical solution.

[0008] The hydraulic casting unit according to the invention is preferably conceived for use in injection molding machines, die casting machines, or thixotropic molding machines, and includes a casting cylinder configured as a differential cylinder, comprising a base chamber near the piston delimiting base and an annular chamber near the piston rod. Furthermore, a low-pressure source is provided, which is particularly connected to the base chamber via a shut-off valve device. Additionally, a hydraulic booster is provided as a pressure booster unit during the pressure holding phase, conceived for promoting the unfolding movement of the casting cylinder, particularly for increasing the pressure in the base chamber. The casting unit further includes a control valve device, which is conceived, particularly during the pre-filling stage, to connect the annular chamber to the base chamber of the casting cylinder via a first pressurized medium flow path in a regenerative loop manner; particularly during the mold filling stage ("injection"), to connect the annular chamber to a pressurized medium tank, particularly a reservoir, via a second pressurized medium flow path; and particularly during the pressure holding stage, to activate a pressure enhancer, conceived to actuate a third pressurized medium flow path leading to the pressure chamber of the pressure enhancer. According to the invention, the valve device is isolated into three directional proportional valves, which can be activated in a decoupled manner. The first directional proportional valve is disposed in the first pressurized medium flow path, the second directional valve is disposed in the second pressurized medium flow path, and the third directional valve is disposed in the third pressurized medium flow path.

[0009] Due to this isolated construction mode, the regeneration motion, injection and pressure accumulation can be controlled independently in open or closed loop, thereby controlling the casting process in an optimized open or closed loop manner with minimal equipment complexity.

[0010] According to the present invention, a three-directional proportional valve, which is simple in terms of equipment and can be started independently, provides the basic functions for implementing the casting unit, namely, the regeneration pre-filling stage, the mold filling stage, and the pressure holding stage. The regeneration movement of the casting cylinder allows the use of a smaller reservoir as a low-pressure source. Due to the lower pressure differential, less cavitation is generated during the regeneration function, and therefore less wear. Because a smaller first-directional proportional valve with better resolution is used during pre-filling, the movement of the casting cylinder can be performed more precisely.

[0011] In one improvement, the main piston of the pressure enhancer defines the pressure chamber of the pressure enhancer by means of its larger end face in the increasing direction, and defines the counter pressure chamber of the pressure enhancer by means of its smaller end face in the opposite direction, especially the annular chamber of the pressure enhancer.

[0012] In one improvement, the pressure booster back pressure chamber can be fluidly connected to the pressure medium tank via a third pressurizing medium flow path, thereby implementing open-loop control of discharge during the pressure holding phase and thereby enabling the pressure booster to start.

[0013] In a variation of this objective, the pressure chamber of the pressure enhancer is fluidly connected to a pressure medium source via a third pressurizing medium flow path, so that the pressure enhancer during the pressure holding phase can be started in this manner by controlling the inflow rate.

[0014] The directional proportional valve is preferably configured to have a closed position. In this closed position, the individual pressurized medium flow paths are blocked or actuated to the closed position.

[0015] In one improvement, a discharge path from the base chamber of the casting cylinder toward the pressurized medium tank is provided or can be configured via first and second directional proportional valves. This discharge path can be actuated or configured via the two mentioned directional proportional valves in particular, based on the detected pressure or time-pressure gradient in the base chamber.

[0016] In one improvement, at least one of the directional proportional valves, at least the first and second directional proportional valves, preferably all three directional proportional valves, is configured as a bidirectional proportional valve, particularly as a 2-position 2-way flow control valve. Each directional proportional valve or 2-position 2-way flow control valve is preferably of the guided control type, particularly of the electro-hydraulic guided control type.

[0017] In one improvement, at least two, preferably all, of the directional proportional valves are designed to have the same construction, or in particular, the same construction, in at least one attribute. Using directional proportional valves with the same construction, or using the same directional proportional valves under boundary conditions, represents a particularly efficient solution in terms of construction, procurement, production, maintenance and operation, and especially cost.

[0018] The term “same construction” in this document may refer to one or more of the properties of a directional proportional valve, such as, for example, type, connector, number of connectors, connector diameter, connection diagram, start-up type, valve body, stroke, switching time and the like.

[0019] The term "identical construction" may alternatively or additionally refer to ratings. In this context, it is advantageous for the first directional proportional valve to have ratings smaller than those of the second and third directional proportional valves, because the volumetric flow of the pressurized medium in the first pressurized medium flow path is relatively smaller than that in the third pressurized medium flow path.

[0020] In one improved embodiment, pressure control in the base chamber is implemented using a venting path and first and second directional proportional valves. This method advantageously controls and / or eliminates pressure peaks or pressure overshoot in the base chamber.

[0021] The pressure accumulation during the pressure holding stage is actually caused by the pressure enhancer with the third directional proportional valve in the control position, especially by means of open-loop or closed-loop control of the leakage from the annular chamber of the pressure enhancer and the open position of the second directional proportional valve, thereby controlling the connection of the pressurized medium between the annular chamber of the casting cylinder and the storage tank.

[0022] In one improvement, the pressure chamber of the pressure enhancer used to accelerate the latter can be connected to a low-pressure source, particularly a hydraulic reservoir, via a shut-off valve or the like. Hereinafter, a second pressurized medium flow path from the pressure enhancer annular chamber toward the pressurized medium tank / to the reservoir is actuated by a third-party proportional valve.

[0023] In a variant of the present invention, the shut-off valve device is configured as a 2-position 2-way active logic system with a pilot valve. The active logic system enables the shut-off or open of the pressurized medium connection between the low-pressure reservoir and the base chamber of the casting cylinder, and is actuated during the pressure holding phase to close in an extremely fast and reliable manner, thereby terminating the mold filling phase in an extremely fast and precise manner.

[0024] In an alternative solution, instead of a shut-off valve device with an active logic system, the device is configured with a shut-off valve located downstream of a low-pressure source, wherein a check valve is positioned between the shut-off valve and the base chamber of the casting cylinder. The shut-off valve blocks and opens the connection to the casting cylinder. The check valve closes the connection when pressure accumulates, either in stage III or the pressure holding stage.

[0025] The closed-loop or open-loop control of the program mentioned above can instead occur by means of a valve, which can be adjusted by means of a servo motor.

[0026] In order to retract the casting cylinder and / or pressure enhancer, and / or to precharge the casting cylinder and / or pressure enhancer, in an improved embodiment, the casting unit has a hydraulic pump configured as a variable displacement pump or a constant displacement pump with a servo motor and a servo inverter, or a variable displacement pump with a three-phase AC motor and a frequency converter, or a variable displacement pump with a three-phase AC motor.

[0027] In this article, pre-filling the annular chamber of the casting cylinder has the effect of avoiding initial vibration during the initial pre-filling stage.

[0028] Therefore, in a preferred embodiment, the casting unit has means for pre-charging the piston side and ring side of the casting cylinder and / or pressure enhancer.

[0029] Preferably, the device for pre-charging consists of a hydraulic pump and a designated shut-off and pre-charging valve configuration.

[0030] In one improvement, the shut-off and pre-charge valve is designed such that the pressure connector of the hydraulic pump can be connected via the shut-off and pre-charge valve to the annular chamber of the pressure enhancer and / or the annular chamber of the casting cylinder and / or the base chamber of the casting cylinder. The annular chamber of the casting cylinder, used for pre-charging or retracting the annular chamber, is supplied with pressurized medium, particularly when the third-party proportional valve is closed.

[0031] In one improvement, the shut-off and pre-charge valve, which has at least a blocked position, is designed as a 4-position 3-way switching valve. Furthermore, the 4-position 3-way switching valve has a first switching position in which the annular chamber of the pressure enhancer and the annular chamber of the casting cylinder are connected to the pressure connector of the hydraulic pump, and in the first switching position, the first pressurized medium flow path, preferably via an unlockable check valve, can be connected to or connected to a pressurized medium tank.

[0032] In one improvement, the shut-off and pre-charge valve has a second switching position in which the base chamber of the casting cylinder is connected to the pressure connector of the hydraulic pump, and in this second switching position, the pre-charge line is connected to the pressurized medium tank, through which the pressure enhancer annular chamber and the casting cylinder annular chamber in the first switching position can be connected to the pressure connector of the hydraulic pump.

Implementation Method

[0033] Figure 1 illustrates the important mechanical components of the hydraulic casting unit 1 of the die casting machine according to the present invention.

[0034] Accordingly, the casting unit 1 has a casting cylinder 10, which is configured as a differential cylinder, and the piston 11 of the casting cylinder is correspondingly configured to have a piston rod 12. The piston 11 and the housing 13 of the casting cylinder jointly define a base proximal chamber 14 and an annular chamber 15, through which the piston rod 12 passes. A casting piston 16, inserted into the injection chamber 18 of the casting sleeve 17, is fastened to the end portion of the piston rod 12 protruding from the housing 13. A filling opening 19 for a liquid or viscous molding compound (hereinafter referred to as melt) is positioned in the casting sleeve 17, and the workpiece to be molded is made of the liquid or viscous molding compound. The casting sleeve 17 is attached to a mold 20, which is typically composed of a movable mold half and a fixed mold half. The two mold halves define a mold cavity 21, also referred to as a cavity, which is configured to correspond to the geometry of the workpiece to be molded. The injection chamber 18 is connected to the mold cavity 21 via the casting pipe 22.

[0035] This type of casting unit 1 is used to introduce the melt into the mold 20, where high speed and subsequent high pressure are required due to the rapid solidification process to completely fill the mold 20 and to compress and compensate for the shrinkage of the material during solidification.

[0036] In the exemplary embodiment of the invention illustrated in FIG2, the casting cylinder 10 is designated as a pressure enhancer 21, also referred to as a multiplier cylinder, which is configured, for example, as a differential cylinder. The main piston 26 is demarcated by the bottom surface of the pressure enhancer pressure chamber 28, and the piston rod 30 passes through the pressure enhancer counter-pressure chamber in the form of an annular chamber 32. The construction of this type of pressure enhancer 24 is known, so further explanation is omitted.

[0037] A hydraulic pump 34 supplies pressurized medium to the described casting unit 1. In the illustrated embodiment, this hydraulic pump is configured as a constant displacement pump and is driven by a speed control motor 38, which may be configured as a servo motor with a servo inverter or a three-phase AC motor with a frequency converter. The pressure connector of the hydraulic pump 34 is connected via a pump line to a shut-off and pre-charge valve 42 configured as a 4-position 3-way valve. In the illustrated initial position centered on the spring or its central position, this shut-off and pre-charge valve 42 blocks the pressurized medium connection between the hydraulic pump 34 and the base chamber 14. By means of two solenoids and hydraulic guide control, the shut-off and pre-charge valve 42 can be switched to two channel positions a and b, in which the shut-off and pre-charge valve 42 and the hydraulic pump 34 function as a device for pre-charging the casting cylinder 10 and the pressure enhancer 24, as will be further described below.

[0038] The annular chamber 15 of the casting cylinder 10 can be connected to the base chamber 14 via a first pressurized medium flow path 23 and a first directional proportional valve 27 disposed therein. In the illustrated embodiment, the latter first directional proportional valve 27 is configured as a 2-position 2-way proportional valve with electro-hydraulic guided control, having a spring-precharged initial position or a blocked position, and is referred to as 2WRCE-4X in the applicant's file and configured as a flow control valve. By actuating electro-hydraulic guided control, the opening profile of the valve 27 is actuated according to an actuation signal, and the annular chamber 15 for regenerative motion is connected to the base chamber 14.

[0039] Furthermore, the annular chamber 15 of the casting cylinder 10 can be connected to the storage tank T via the second pressurized medium flow path 44, in which the second directional proportional valve 46 is disposed. The second directional proportional valve 46 has the same construction as the first directional proportional valve 27 in the valve type direction, but has a higher rating than the latter, because the volumetric flow rate of the pressurized medium via the second directional proportional valve 46 is greater than the volumetric flow rate during the regeneration motion performed via the first directional proportional valve 27. The second directional proportional valve 47 is similarly configured as an electro-hydraulic guided control 2 / 2 flow control valve, which blocks the connection of the pressurized medium to the storage tank T in its initial position, and actuates the opening profile toward the storage tank T by actuating the electro-hydraulic guided control according to the actuation signal.

[0040] The second pressurized medium flow path 44 is fluidly connected to the pre-charge line 50 via a check valve 48 that is open to the second pressurized medium flow path 44. The pre-charge line 50 is blocked at the spring-loaded initial position of the check valve 48.

[0041] The pump line 40 between the third directional proportional valve 29 and the pressure enhancer annular chamber 32 leads to the third pressurized medium flow path 25. A check valve 70, opening toward the pressure enhancer annular chamber 32, is located in the pump line 40, between a branch of the pre-charge line 50 from the pump line 40 and this nozzle. When there is sufficient pressure in the pump line 40 and the pre-charge line 50, the two check valves 48 and 70 open, supplying the annular chambers 15 and 32 of the casting cylinder 10 and the pressure enhancer 24. In this way, the casting cylinder 10 and the pressure enhancer 25 can retract, and the back pressure required for pre-charging the casting cylinder 10 and the pressure enhancer 24 can accumulate in the respective annular chambers 15 and 32. For this purpose, the shut-off and pre-charge valve 42 has a first switching position a, in which the pressure connector P of the hydraulic pump 34 is connected to the pump line 40 and the pre-charge line 50, and in this first switching position, the first pressurized medium flow path 23 having a reservoir can be connected to or connected to the pressurized medium tank T by means of an unlockable check valve 72.

[0042] The pressure at the output end of the hydraulic pump 34 can be defined in a known manner by means of a pressure relief valve that opens toward the reservoir T.

[0043] According to the present invention, the pressure enhancer 24 and the casting cylinder 10 are assigned a valve device, which is isolated into three flow control valves 27, 46 and 29, which can be activated independently of each other and, in each case, are configured as a continuously adjustable electro-hydraulic pilot control valve with two connectors.

[0044] A 2-position 2-way valve for guidance control constitutes the active logic system 41. Guidance control is executed by a pilot valve 52, which is configured as a 3-position 2-way valve. The input connector A of the active logic system 41 is connected to the low-pressure reservoir 56 via a low-pressure reservoir line 54. Connectors A and B of the active logic system 41 can also be assembled in reverse order. The output connector B of the active logic system 41 is connected to the base chamber 14 of the casting cylinder 10.

[0045] The potential construction of the active logic system 41 is known from the disclosures DE 10 2017 220 836 A1 and DE 10 2005 035 170 B4 cited at the beginning of the specification, such that only the construction elements relevant to the understanding of the present invention will be explained herein, and reference will be made in other ways to the prior art. Thus, the active logic system 41 has a stepped main piston 60 that is pre-charged against a valve seat 58 by pressure acting on face A5 from the low-pressure reservoir ND via a switching pilot valve 52, and blocks the pressurized medium connection between connectors A and B of the active logic system 41, and thus between the low-pressure reservoir line 54 and the pressure line 59. The pressure line 59 leads to the base chamber 14 of the casting cylinder 10. The main piston 60 has an inner bore from face A5 toward face A3, thereby ensuring pressure balance between face A5 operating in a closed manner and face A3 operating in an open manner. The active logic system 41 can be turned on and off in a targeted manner via control surface A4. In this document, surface A4 can be selected to be greater than the difference A5-A3, or the control pressure of the memory ND can be set accordingly higher in order to reliably turn on the active logic system 41.

[0046] The reservoir line 62 is connected to the reservoir connector of the pilot valve 52, and the input connector of the pilot valve 52 is connected to the control reservoir or the low-pressure reservoir ND via the line 64. By actuating the solenoid of the pilot valve 52, the pilot valve can be adjusted to the switching position against the force of the spring. In the switching position, the annular control chamber of the active logic system 41 defined by face A4 is connected to the low-pressure reservoir ND, so that the main piston 60 is lifted from the valve seat 58 due to the pressure acting on the annular end face A4, and actuates the fluid connection between connectors A and B.

[0047] An active logic system 41 is embedded such that flow can pass through the active logic system 41 with minimal pressure loss, and when actuated accordingly by the pilot valve 52, it closes with minimal switching time and in a highly reproducible manner. The stroke of the active logic system 41 can also be limited to optimize subsequent shutdown behavior. Due to this specific construction of the active logic system 41, even at high ratings, only a small amount of control fluid flow is required to open and close the active logic system 41 quickly and reproducibly.

[0048] Furthermore, operational reliability is enhanced by actively opening and closing the active logic system 41 using the pilot valve 52 and reliably maintaining the active logic system 41 closed by means of the reservoir pressure. In this document, the closing conditions can be freely selected by actively closing the active logic system 41. This closing can occur, for example, based on pressure, load force, movement path, movement speed, etc.

[0049] As illustrated in Figure 2, the low-pressure reservoir 56 can be connected to the pressure chamber 28 of the pressure enhancer via a 2-position 2-way seat valve (hereinafter referred to as the reservoir shut-off valve 66, which is guided and controlled by the pilot control valve 68). For this purpose, the pressurizing medium itself is dissipated from the low-pressure reservoir 56. The chamber downstream of the reservoir shut-off valve 66, in the pre-charge initial position of the pilot control valve 68 (hereinafter operated in a closed manner), is subjected to pressure surges from the low-pressure reservoir 56, and in the switching position, is subjected to pressure surges from the reservoir tank. Thus, the reservoir shut-off valve 66 connects the low-pressure reservoir 56 to the pressure chamber 28 of the pressure enhancer. Therefore, in this switching position, the pressure enhancer 24 is charged in the promoting direction.

[0050] The functional modes of casting unit 1 illustrated in Figure 2 during phases I to III described at the beginning will now be explained.

[0051] To prevent pressure waves along the direction of the casting cylinder 10 from being generated during the initial movement of the casting cylinder 10 in the pre-filling stage, which would cause initial vibration, the casting cylinder 10 is pre-charged before the start of the pre-filling stage I, before the active logic system 41 (also known as the reservoir shut-off valve) is opened. This occurs because, in the case of the retracted casting cylinder 10 and pressure enhancer 24, the annular chamber 15 of the casting cylinder 10 and the pressure enhancer annular chamber 32 of the pressure enhancer 24 can be pre-charged to the maximum pumping pressure by means of the hydraulic pump 34 and the shut-off pre-filling valve 42 activated to its first switching position, and by means of the open check valves 48 and 70. In this manner, the first directional proportional valve 27, the second directional proportional valve 46, and the third directional proportional valve 29 are closed to prevent short circuits toward the reservoir. The shut-off and pre-filling valve 42 preferably has a check function.

[0052] In the subsequent steps, according to FIG. 1, the melt is filled into the injection chamber 18 of the casting sleeve 17 through the filling opening 19, and the pre-filling stage I is initiated. For this purpose, the hydraulic pump 34 is actuated by the ramp function, and the base chamber 14 of the casting cylinder 10 is charged to the reservoir pressure value of the low-pressure reservoir 56 by the second switching position b of the shut-off and pre-fill valve 42. Therefore, the casting cylinder 10 unfolds slowly without any initial vibration of pre-filling in the annular chamber 15 until the fluid contained in the annular chamber 15 is compressed and there is a force balance on the piston 11. Importantly, due to this control action, the pressure in the base chamber 14 of the casting cylinder 10 is equal to the pressure in the low-pressure reservoir 56 in a vibration-free manner. Subsequently, the low-pressure reservoir 56 can be connected to the base chamber 14 via the active logic system 41 (reservoir shut-off valve), and the low-pressure reservoir 56 can be connected to the pressure booster chamber 28 via the reservoir shut-off valve 66.

[0053] This method is unnecessary if the pump 34 can generate sufficiently high pressure. In the case of a correspondingly pre-charged annular chamber 15, the low-pressure reservoir 56 can also be switched to the piston chamber 14 by the active logic system 41.

[0054] Depending on the customer’s requirements, a common piston reservoir can be used for casting cylinders and pressure enhancers, or a dedicated piston reservoir can be used in each case.

[0055] Subsequently, the first directional proportional valve 27 is actuated by guide control, so that the pressurized medium displaced from the annular chamber 15 is directly supplied to the base chamber 14 in a regenerative circuit manner. This allows the casting cylinder 10 to start and move smoothly (without vibration, and in a regenerative and controlled manner). Therefore, the melt is accelerated and displaced in the direction of the mold cavity 21 according to FIG. 1. The above situation occurs until the melt reaches the mold feed orifice and the pre-filling stage I is completed.

[0056] Due to the regenerative movement of the casting cylinder 10 in the pre-filling stage I, less pressurized medium is removed from the low-pressure reservoir 56, allowing the low-pressure reservoir 56 to have a smaller volume than in a conventional solution without regenerative movement. Because the pressure loss caused by the differential circuit is smaller, and because the first directional proportional valve 27 is less than one or two rated values, the resolution of the casting cylinder speed can be improved, allowing the casting cylinder 10 to move at a lower speed and with improved reproducibility.

[0057] Another advantage of regenerative motion is that, due to the lower pressure loss on the first directional proportional valve 27, and because the pressurized medium from the annular chamber 15 does not flow out against the reservoir pressure (0 Pa) but against the pressure in the low-pressure reservoir 56, there is less cavitation on the valve 46, on the piston 11, and on the housing 13 of the casting cylinder 10 and the associated control block, and therefore less wear.

[0058] According to the present invention, the pressure in the base chamber 14 can be actively affected in the sense of pressure reduction or pressure release by actuating the first directional proportional valve 27 and the second directional proportional valve 46 (which are arranged in series with the former). For example, pressure overshoot in the base chamber 14 can therefore be easily eliminated in this path.

[0059] According to the present invention, the pressure in the base chamber 14 can also be affected by a third directional proportional valve 29, which can be activated completely independently of the first directional proportional valve 27 and the second directional proportional valve 46. Due to the independent pressurized medium flow paths 23, 44, 25 and valves 27, 46, 29, more precise and dynamic control of the pressure in the base chamber 14 is achieved.

[0060] Once the melt reaches the mold inlet orifice, the actual mold filling process (stage II) begins. Regeneration continues while the mold is filled (injected) with a low mold filling force. Therefore, at the moment the melt reaches the mold inlet orifice, for example by a jump function, the first directional proportional valve 27 is adjusted to the position where the pressurized medium connects the annular chamber 14 and the base chamber 15, so that the melt is injected into the mold 20 at a high injection rate (up to 10 m / s). In this text, the operation continues in a regeneration manner; in other words, the pressurized medium displaced from the annular chamber 15 is supplied to the incremental base chamber 14.

[0061] This type of regeneration method has the advantage that less pressurized medium must be removed from the low-pressure storage 56 compared to conventional solutions.

[0062] When injection occurs under higher mold filling force, at the moment the melt reaches the mold feed orifice, the first directional proportional valve 27 moves to its closed position, for example, by a jump function, thereby interrupting the pressurized medium connection between the annular chamber 15 and the base chamber 14. Parallel to this, the outflowing second directional proportional valve 46, for example, opens to a predetermined opening section toward the reservoir T by a jump function. This situation results in the melt being injected into the mold cavity 21 at a high injection rate, wherein, unlike the method under low mold filling force, the operation does not occur in a regenerative manner, and therefore the maximum force of the casting cylinder 10 can be utilized.

[0063] In principle, a hybrid form may also be considered, wherein the first directional proportional valve 27 is adjusted to its blocked position only during stage II according to the force of the load.

[0064] Stage II can also be fully operated in a regenerative mode. However, this is contingent upon the regenerative mode being able to achieve the required force for the load in Stage II. In this case, the second directional proportional valve 46 can be replaced by a quick-switching valve for releasing the annular chamber 15 in Stage III.

[0065] Once the mold cavity 21 is completely filled, the transition to stage III occurs. To this end, at the end of mold filling stage II, a third directional proportional valve 29 is actuated in the direction of opening of the connection between the pressure enhancer annular chamber 32 and the reservoir T by guide control. The second directional proportional valve 46 opens simultaneously. The pressure release setting in the pressure enhancer annular chamber 32 accelerates the main piston 26, thus accumulating high pressure in the base chamber 14, causing the piston 11 to be subjected to high-pressure impact and the melt to be ultimately compressed. Once the desired holding pressure is reached, the second directional proportional valve 29 is reset in the closing direction by the pressure regulator. If the closing of the second directional proportional valve 29 does not occur quickly enough, the pressure overshoot in the base chamber 14 can be eliminated by actuating the aforementioned release path, thus actuating the directional proportional valves 27 and 46 towards the reservoir T.

[0066] Because the first 2-way proportional valve 27 has a dual function of controlling regeneration and pressure in the base chamber 14, it can be used in place of the 3-way proportional valve (50% connection between A and T; 50% connection between A and P) with a rating that is less than at least one of the ratings of the 3-way proportional valve (100% A and T). The smaller rating results in improved dynamics.

[0067] The casting unit described has the advantage of allowing the pressurized medium removed from the annular chamber 15 by the regenerative motion of the casting cylinder 10 to be directly supplied to the base chamber 14 of the casting cylinder 10 via the first directional proportional valve 27. A further specific feature is the active shutdown of the active logic system 41 at the end of stage II.

[0068] The active logic system can also be replaced by a shut-off valve and an external check valve.

[0069] A casting unit is disclosed in which the casting cylinder in the pre-filling stage can be moved regeneratively by means of a first flow control valve. Furthermore, this first flow control valve has the function of controlling the pressure in the base chamber of the casting cylinder. The casting cylinder in the mold filling stage can move regeneratively or non-regeneratively for programmed control by means of a second flow control valve. In addition, an amplification unit configured as a pressure enhancer is activated by a third flow control valve during the pressure holding stage. The pressure in the base chamber can also be controlled by the third flow control valve. All the aforementioned flow control valves can be activated in a decoupled manner. In combination, these flow control valves enable extremely precise and dynamic control of the pressure in the base chamber, representing a superior solution compared to solutions with 3-way flow control valves. [Simplified Explanation of the Diagram]

[0071] The preferred exemplary embodiments of the present invention will be explained in more detail below with the aid of schematic diagrams, wherein: [Figure 1] shows a schematic diagram of a casting unit; and [Figure 2] shows a simplified hydraulic circuit diagram of an exemplary embodiment of the casting unit.

Claims

1. A hydraulic casting unit for a molding machine, particularly an injection molding machine, a die casting machine, or a thixotropic molding machine, the hydraulic casting unit having a casting cylinder (10) configured as a differential cylinder and having a piston (11) defining a base proximal chamber (14) and a piston rod proximal annular chamber (15); and having a low-pressure source (56) that is operable to the base chamber (14) for one of the casting cylinders (10); and having a pressure enhancer (24) configured to increase the pressure in one of the base chambers (14) during a low-pressure phase;It also has a control valve device by which the annular chamber (15) can be fluidly connected to the base chamber (14) via a first pressurized medium flow path (23), and fluidly connected to a pressurized medium tank (T) via a second pressurized medium flow path (44). Furthermore, via the control valve device, a third pressurized medium flow path (25) leading to one of the pressure booster back pressure chambers (32) of the pressure booster (24) can be actuated or configured to start the pressure booster (24). The valve device is characterized by being isolated into three directional proportional valves (27, 46, 29), which can be started in a mutually decoupled manner, wherein one of the first directional... A proportional valve (27) is disposed in the first pressurized medium flow path (23), a second directional proportional valve (46) is disposed in the second pressurized medium flow path (44), and a third directional proportional valve (29) is disposed in the third pressurized medium flow path (25). The casting unit has a drain path, which is configured to allow pressure control in the base chamber (14) to proceed from the base chamber (14) toward the pressurized medium tank (T) via the first directional proportional valve (27) and the second directional proportional valve (46) based on a detected pressure or time pressure gradient in the base chamber (14). Pressure control in the base chamber is achieved by means of the drain path and the first and second directional proportional valves. The casting unit has a hydraulic pump (34) configured as a variable displacement pump, or configured as a constant displacement pump with a servo motor and a servo inverter, or configured as a variable displacement pump with a three-phase AC motor and a frequency converter, or configured as a variable displacement pump with a three-phase AC motor. The casting unit has a shut-off and pre-charge valve (42) configured to connect the pressure connector of the hydraulic pump (34) to the pressure booster back pressure chamber (32) and / or to the annular chamber (15) of the casting cylinder (10) and / or to the base chamber (14) of the casting cylinder (10). The shut-off and pre-charge valve (42) is designed as a 4-position 3-way switching valve, having a first switching position (a). In this first switching position, the pressure booster back pressure chamber (32) and the annular chamber (15) of the casting cylinder (10) are connected to the pressure connector (P) of the hydraulic pump (34). In this first switching position, the first pressurized medium flow path (23) is preferably connected to or via a releaseable check valve (72) to the pressurized medium tank (T).

2. The casting unit of claim 1, wherein one of the main pistons (26) of the pressure enhancer (24) defines a pressure enhancer pressure chamber (28) by means of its larger end face effective in the increasing direction, and defines a pressure enhancer counter-pressure chamber (32) by means of its smaller end face effective in the opposite direction, in particular a pressure enhancer annular chamber, wherein the pressure enhancer counter-pressure chamber (32) is fluidly connected to a pressure medium tank (T) by means of the third pressurizing medium flow path (25).

3. The casting unit of claim 1 or 2, wherein at least one of the directional proportional valves (27, 29, 46) is configured as a preferred electro-hydraulic guided control 2-position 2-way flow control valve.

4. The casting unit of claim 1 or 2, wherein at least the second directional proportional valve (46) and the third directional proportional valve (29), or at least two of the first to third directional proportional valves (27, 29, 46), preferably all directional proportional valves (27, 29, 46), have the same construction.

5. The casting unit of claim 2, wherein the pressure chamber (28) of the pressure enhancer can be connected to a low-pressure source or the low-pressure source (56) by means of a reservoir shut-off valve (66).

6. The casting unit of claim 5, wherein the shut-off valve device is configured as a 2-position 2-way active logic system (41) having a pilot valve (52).

7. The casting unit of claim 1 or 2, having a device (34, 42) for pre-charging the casting cylinder (10) and / or the pressure enhancer (24).

8. The casting unit of claim 1, wherein the shut-off and pre-charge valve (42) has a second switching position (b), in which the base chamber (14) is connected to the pressure connector (P) of the hydraulic pump (34), and in which a pre-charge line (50) is connected to the pressurized medium tank (T), by which the pressure enhancer back pressure chamber (32) in the first switching position (a) and the annular chamber (15) of the casting cylinder (10) can be connected to the pressure connector (P) of the hydraulic pump (34).

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