Active logic valve with stroke setting upon opening and dynamic closing

Abstract

The invention relates to a device for filling a casting mould of a hydraulic casting unit in a molding machine, comprising an active logic valve (41), which has an input that can be connected to a pressure accumulator (15) and an output that can be connected to a casting cylinder. According to the invention, a stroke measuring system (60) is provided, which is located on a logic piston of the active logic valve (41), and a proportional auxiliary valve (10) is provided for the controlled opening, closing and positioning of the active logic valve (41) by means of a control surface (A4) of the logic piston provided on the active logic valve (41).

Description

Technical Field

[0001] The present disclosure relates to an active logic valve which can be used as a accumulator shut-off valve, in particular for die-casting machines, injection molding machines or thixo-molding machines and the like. Background Art

[0002] In the aforementioned methods, such as those described in DE 10 2017 220 832 A1, a liquid or viscous material is generally introduced into a mold by a casting unit, where the material then solidifies or hardens. To this end, the material must be introduced into the mold at a high speed and, after filling, must remain loaded in the mold at a high pressure in order to completely fill the mold before solidification and to compensate for shrinkage.

[0003] According to the aforementioned DE 10 2017 220 832 A1 Figure 1 , Figure 3 and Figure 4 Corresponding and therefore presenting the prior art Figures 1 to 3 , the general filling process for such molds is first described in three stages.

[0004] After the melt has been injected into the casting sleeve 17 through the injection opening 19, phase 1, also called the pre-filling phase, begins. The casting piston 16 starts without impact and initially moves forward slowly. The injection opening 19 of the casting sleeve 17 is passed by the casting piston 16 and closed; the air in the casting sleeve 17 escapes through the (not shown here) riser until the casting sleeve 17 is filled and the melt reaches the mold gate 22.

[0005] In phase 2, the melt is accelerated by the pouring piston 16 to the injection speed at maximum acceleration and fills the mold 20 at the highest possible constant speed (mold filling). At the end of phase 2, the storage shut-off valve (to be explained more precisely later in the detailed embodiment, not yet shown here) must then be closed as quickly as possible so that the pressure build-up can begin without time loss (cooling).

[0006] When the storage shut-off valve is closed, pressure holding is implemented by a pressure intensifier (multiplier) or a high-pressure storage. In the third stage (also called the pressure holding stage), the casting material is compressed with high pressure until the last mold cavity and the material shrinkage is compensated.

[0007] For further prior art, see, for example, the publications DE 10 2020 201 216 B4, DE 10 2017 220 836 A1 or DE 10 2017 220 832 A1.

[0008] As already described above with respect to phase 2, the storage shut-off valve should be closed as quickly as possible so that a high pressure can be built up within a few milliseconds during the pressure holding phase. In order to achieve these two objectives more efficiently, the inventors have developed the following solution starting from DE 10 2017 220 832 A1. Summary of the invention

[0009] An active logic valve is included in the control module as a device for filling a casting mold, which connects the pressure reservoir to the casting cylinder. A travel measuring system is provided at the logic piston of the active logic valve. The active logic valve is also controlled by a proportional pilot valve, which serves to open and position the logic piston via a control surface provided at the active logic valve.

[0010] When controlled accordingly by a proportional pilot valve, the active logic valve (hereinafter sometimes also referred to as "active logic unit") can be opened slowly and in a controlled manner, wherein a stroke measurement system additionally provides feedback on the degree of opening. Furthermore, in the case of low injection speeds, i.e. small components to be manufactured, it can happen that the cylinder of the piston accumulator begins to oscillate during acceleration and these oscillations are then transmitted to the casting cylinder. This results in a non-uniform injection of the casting cylinder. According to the invention, the oscillations can be reduced in the following way: in the case of low injection speeds, the active logic valve in the inlet of the casting cylinder is not completely opened. The resulting counterpressure reduces the oscillations of the piston accumulator. Based on the stroke measurement system, the piston of the active logic valve can be opened repeatedly to a predetermined position in order to reduce or completely prevent such oscillations.

[0011] Preferably, the active logic valve according to the invention can flow through it in the fully open state with minimal pressure loss. The active surface makes it possible to hold the logic piston in the end position so that no spring force acts during flow. The structure according to the invention can dispense with non-return valves used in other arrangements for faster closing, since the active logic valve designed according to the invention can be opened and closed repeatedly within a few milliseconds, making non-return valves superfluous. As a result, the spring force of the non-return valve does not have to be overcome during outflow, so that pressure losses are minimized.

[0012] In the open state, virtually the entire reservoir pressure can therefore be applied to the casting cylinder and optimally accelerate it during injection. This can advantageously be achieved by connecting the spring chamber of the active logic valve via a bore in the valve to a connection of the pressure reservoir in such a way that pressure compensation occurs between these spaces.

[0013] For opening, the active control surface of the active logic valve is loaded with pressure via a proportional pilot valve. The pressure must be higher than the spring force and the flow force in order to reliably keep the active logic valve open. In order to quickly close the active logic valve, the pilot valve is opened together with the pilot valve to the tank as a function of the stroke of the casting cylinder detected by the (additional) stroke measurement system. The active logic valve is thus closed within a few milliseconds. If, as described above, the piston is only partially opened at low injection speeds, the active logic valve can be closed even faster before the aforementioned pressure buildup for "holding pressure". BRIEF DESCRIPTION OF THE DRAWINGS

[0014] in:

[0015] Figure 1 , Figure 2 and Figure 3 A diagram is shown for illustrating the system structure according to the prior art and for explaining the basic sequence of the casting process;

[0016] Figure 4 The diagram shows a simplified example for explaining a system configuration having an active logic valve used according to the invention and a proportional valve for actuating the active logic valve. DETAILED DESCRIPTION

[0017] Next, based on Figure 4 Embodiments of the present disclosure are described.

[0018] Firstly, the function of an active logic valve 41 is explained which can be controlled by means of the proportional valve 10 according to the invention and which is arranged in the inlet of the casting cylinder 11 (coming from the pressure reservoir 15 ).

[0019] The pressure chamber on the bottom side of the pouring cylinder 11 can be directly connected to the pressure connection of the metering pump 20 via a 2 / 2-way proportional valve (acting as a flow control valve 1) that can be directly actuated electromagnetically and is closed without current, and a 4 / 3-way directional valve 16. The pressure chamber on the bottom side of the pouring cylinder 11 can also be connected to the reservoir 15 via a 2 / 2-way inlet valve 41 that is designed as an active logic unit. The valve is a seat valve and has a movable main piston 42 that is designed as a stepped piston, which may be connected to the reservoir 15. Figure 4The main piston 42 is inserted into the mounting hole 43 together with a fixed mounting sleeve (not shown in the figure); a first connection A, which is permanently connected to the high-pressure storage device 15 in terms of fluid; and a second connection B, which is permanently connected to the pressure chamber 14 of the casting cylinder 13 in terms of fluid. The first connection A is a so-called axial connection, because the pressure existing at the first connection loads the first end face 44 of the main piston 42. Usually, the axial connection leads into the mounting hole or the mounting sleeve in the axial direction of the mounting hole or the mounting sleeve. The second connection B is a lateral connection. The main piston 42 does not provide a load surface for the pressure existing in the connection. The surrounding edge at the first end face forms a control edge of the main piston 42, which can be supported on the conical surface of the mounting hole or the mounting sleeve if necessary, then the 2 / 2-way installation valve 41 is closed, and can be lifted from the conical surface, then the 2 / 2-way installation valve is opened.

[0020] The stepped main piston 42 has a flange 45, which has a larger diameter than the first end face 44 of the main piston 42 and the section adjacent to the end face 44. The flange 45 is located in the hole 46 of the control cover 47 of the 2 / 2-way insert valve 41 and forms a rear control chamber 49 with the second end face 48 in the hole 46 and an annular control chamber 51 with the annular surface 50. The two control chambers 49 and 51 are sealed relative to each other by a sealing portion that is not shown in more detail around the flange 45. In addition, the control chamber 51 is sealed relative to the lateral connection B by the sealing portion. A spring 52 is arranged in the rear control chamber 49, which loads the main piston 42 in the closing direction. The control surface A5 in the rear control chamber 49 is defined by the flange 45.

[0021] The 2 / 2-way inlet valve 41 has a pilot valve 10, which is configured as a 4 / 4-way proportional valve and occupies a rest position under the action of a compression spring 56, in which the pilot valve connects the annular control chamber 51 to the tank 57 via the auxiliary valve 9 and thus relieves the pressure. In addition to the position monitoring shown, the auxiliary valve 9 can also be provided with a stroke limitation. By energizing the electromagnet 58, the pilot valve 10 can be switched to a switching position, in which the pilot valve connects the control chamber 51 to the hydraulic accumulator 59 and closes the auxiliary valve 9 (keeps it closed). The annular control chamber 51 is then loaded with the pressure to which the hydraulic accumulator 59 is loaded. The pressure present in the control chamber 51 generates the following force at the annular surface 50, which engages the main piston 42 in the sense of opening or keeping the 2 / 2-way inlet valve or active logic valve 41 open. The main piston can then be loaded in the opening direction at the annular surface 50 by the pressure in the hydraulic accumulator 59. The annular surface 50 is referred to as the second control surface A4 here.

[0022] The bore 65 axially penetrates the main piston 42 as a pressure connection, which connects the rear control chamber 49 to the connection A, so that the pressure to which the pressure accumulator 15 is applied is always present at the two end faces 44 and 48 of the main piston. A force is generated at the pressure differential surface 66 (the end face 48 is larger than the end face 44 by this differential surface, and the differential surface is as large as the annular surface 50), which engages the main piston 42 in the sense of closing or keeping the 2 / 2-way inlet valve 41 closed. The main piston 42 can then be loaded in the closing direction by the pressure of the pressure accumulator 15 that is permanently present at the connection A at the differential surface 66 between the end face 48 and the end face 44. The differential surface 66 is to be referred to here as the first control surface A5.

[0023] Therefore, if the pilot valve 10 is in its rest position and the control surface 50 is therefore relieved of pressure, the following forces are present at the main piston 42. The low pressure generates a force in the opening direction at the end surface 44 and a force in the closing direction of the main piston 42 at the end surface 48 of the main piston. This results in a force in the closing direction of the main piston 42, which is generated by the low pressure at the first control surface 66. In addition, a force in the closing direction of the main piston 42 is generated by the spring 52. In the rest position of the pilot valve 10, the main piston 42 is then in its closed position or is held in the closed position, wherein the force generated by the pressure loading and acting in the closing direction is independent of whether and what pressure is present in the pressure chamber 14 of the casting cylinder 13.

[0024] In order to lift the main piston 42 from its seat and thus to open and keep the 2 / 2-way insert valve 41 open, the pilot valve 10 is switched so that the second control surface A4 is now additionally loaded with the pressure in the hydraulic accumulator 59 and generates a force that acts in the opening direction of the 2 / 2-way insert valve 41. In order to open and keep the valve open, this force must be greater than the force that acts in the closing direction. When the low pressure is then, for example, a maximum of 160 bar (bar) and the pressure equivalent of the spring 52 is thirty bar, the second control surface A4 (if it is, for example, the same size as the first control surface A5) must be loaded with a pressure greater than 190 bar. The hydraulic accumulator 59 must be loaded with a corresponding level. It should be noted that in the above observations, for the sake of simplicity, the flow forces that usually act in the closing direction of the valve are not taken into account.

[0025] Alternatively, the second control surface A4 can also be made larger than the first control surface A5. A lower pressure than described above is then required to open the 2 / 2-way inlet valve 41. A low-pressure reservoir (not shown) can then be used as a pressure source for the control pressure.

[0026] exist Figure 4In the figure, the main piston 42 of the 2 / 2-way inlet valve is shown in the open position. Conversely, the illustrated position of the pilot valve 10 would correspond to the closed position of the main piston 42. The positions corresponding to each other can be easily assigned to a person skilled in the art.

[0027] If the 2 / 2-way inlet valve 41 is fully opened immediately at the beginning of the pre-filling phase for starting the pouring cylinder 10, a pressure surge may occur in the direction of the pressure chamber 14 of the pouring cylinder 10, which may lead to a starting shock that is disadvantageous for the pouring process. In order to also reliably avoid such a starting shock, the 2 / 2-way inlet valve 41 is provided with an additional stroke measuring system 60 for the stepped main piston 42 that acts as a logic piston. The valve 41 can be opened slowly and controlled (or adjusted by the stroke measuring system 60) by means of the proportional pilot valve 10 and the stroke measuring system 60 for the logic piston 42. If the flow control valve 1 between the ring side and the piston side of the pouring cylinder 11 is opened in parallel, the pouring cylinder can be started without shock, without prestressing the ring side, because the piston side is loaded with a predetermined lower pressure by the active logic valve, so that a force difference that can be set as desired and lower occurs during the start. In addition, the flow control valve 1 can adjust the speed throughout the entire phase 1.

[0028] Furthermore, the invention can be used to prevent the cylinder of the piston reservoir 15 from oscillating during acceleration and transmitting the oscillations to the casting cylinder 11 at low injection speeds (during injection). Such oscillations would prevent a stable injection speed from being achieved. The oscillations can be reduced or prevented by not fully opening the active logic valve 41 in the inlet of the injection cylinder for low speeds and dampening the oscillations of the piston reservoir by the resulting counterpressure. The active logic valve 41 has a stroke measuring system 60 for checking a reliable position (active logic closed). Using the proportional directional valve 10 according to the invention and by feedback from the stroke measuring system 60, the piston of the active logic valve 41 can be opened in a controlled manner to a previously tested position during opening in phase 1, thereby preventing or reducing oscillations at low injection speeds.

[0029] The active logic valve 41 is usually designed in such a way that it can be traversed with minimal pressure loss and can be closed with high repeatability with minimal switching time when the auxiliary valves 9 and 10 are correspondingly actuated. For this purpose, the rear control chamber 49 with the control surface A5 is connected to the connection A by means of the internal bore 65. This ensures pressure compensation of this space. In addition, when the active logic valve is open, the oil can be discharged against a low resistance, because the active logic valve holds the logic piston in the end position via the active surface, so that the spring force has no effect during the flow. In addition, there is no additional non-return valve, whose spring force must be overcome, as in the prior art.

[0030] The active logic valve can be opened or closed in a targeted manner via the pilot valve 10 and the second control surface A4. Here, the control pressure is correspondingly selected to be higher in order to reliably open the valve.

[0031] For rapid closing, the pilot valve 9 is opened in conjunction with the pilot valve 10 to the tank as a function of the stroke of the pouring cylinder 11 and the active logic valve 41 is closed within a few milliseconds.

[0032] If, at low injection speeds, the piston of the active logic valve 41 is only partially opened, the active logic valve 41 can be closed even more quickly before the pressure buildup in phase 3 .

[0033] Overall, the structure of the invention offers the following advantages compared to what is considered to be the closest prior art from DE 10 2017 220 832 A1.

[0034] It can start without shock without prestressing the piston side. The oscillation of the injection piston can be reduced or prevented at low injection speeds. The pressure building time can be reduced because only a small control oil flow is required even with large nominal dimensions based on the special structure of the active logic valve 41 (the connection between the spring chamber surface A5 and the surface A3 and the small active control surface A4) to quickly and repeatably open or close the valve. The pressure building time is further reduced at low injection speeds because the active logic is only partially opened and thus closed more quickly. The active opening and closing performed by the auxiliary valve is also beneficial to safety. The injection-storage pressure is also reliably maintained or maintained. The position is monitored by a stroke measurement system, which can also be set at the casting cylinder 11 and the auxiliary valve 10 in addition to the stroke measurement system at the active logic valve 41. By actively closing the active logic valve 41, the conditions for closing can be freely selected depending on any parameters, such as pressure, force, stroke, speed, that is, in a functional manner (f(p, F, s, v, ...,)). As a result, the proportional valve 10 can also be switched before the mold is filled in order to compensate for the switching time or to already initiate a closing process of the active logic valve 41 .

Claims

1. A control module for filling a casting mold of a hydraulic casting unit in a molding machine, the control module comprising the following parts: An active logic valve (41), the active logic valve having: A first connector (A) connectable to a pressure storage device (15); A second connector (B) connectable to the pouring cylinder (11), Features a travel measurement system (60) at the logic piston of the active logic valve (41), and A proportional auxiliary valve (10) is used to controllably open, close and position the active logic valve (41) through a control surface (A4) of the logic piston disposed at the active logic valve (41).

2. The control module according to claim 1, wherein: The active logic valve (41) comprises a first control surface (A5) as a boundary surface of a spring chamber, in which a spring is arranged such that it presses the logic piston into a closed position of the active logic valve (41) in a non-pressure-loaded state.

3. The control module according to any one of claims 1 or 2, wherein: A pressure connection (65) is provided between the spring chamber and a first connection (A) of the active logic valve (41).

4. The control module according to any one of claims 1 to 3, wherein: The control module is capable of partially opening the active logic valve (41) by means of the proportional pilot valve (10).

5. The control module according to any one of claims 1 to 4 further has an additional auxiliary valve (9), which opens the connection between the active logic valve (41) and the tank based on the control performed with the aid of the auxiliary valve (10) depending on the stroke of the casting cylinder (11) so as to close the active logic valve more quickly.

6. A hydraulic casting unit having a control module according to any one of the preceding claims, the hydraulic casting unit further comprising: A casting mold with a casting cylinder (11); a pressure booster (12) or a high pressure accumulator; and Pressure storage device (15), in, The device, the pouring cylinder (11) and the pressure booster (12) or the high-pressure accumulator are arranged in such a way that the pouring cylinder (11) can be loaded with pressure via the active logic valve (41) and the flow control valves (1, 2) so that it can be started without shock.

7. The hydraulic pouring unit according to claim 6, wherein: A non-return valve is omitted in the outflow of the active logic valve (41).

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