Device for producing process air and method for demoulding moulded parts for injection-moulding machines

Abstract

The invention relates to a device (100) for providing process air at at least two different pressure levels for an injection-moulding machine with an injection mould (10). The device (100) has a series arrangement of two valves (Ia, IIa; Ib, IIb), wherein the first valve (Ia; Ib) is connected on the one hand to a first pressure source (pI) at a first pressure level and on the other hand to an air duct (11a; 11b), which leads into the injection mould (10), and the second valve (IIa; IIb) is connected to a second pressure source (pII) at a second pressure level and also a venting line (12), wherein the first and second valves (Ia, IIa; Ib, IIb) are designed and activatable in such a way that either the first pressure or the second pressure can be respectively applied to the air duct (11a; 11b). Also proposed are an injection-moulding machine with such a device (100), a method for demoulding moulded parts with the aid of such a device (100) and also a use of such a device (100).

Description

[0001] Description

[0002] Device for generating process air and method for demoulding moulded parts for injection moulding machines

[0003] TECHNICAL FIELD OF THE INVENTION

[0004] The invention relates to a fluid power device for applications on injection molding machines which require process air and which have high demands on the reproducibility of demolding. This is particularly the case in the production of closure caps, but it can also relate to other applications. The present invention relates in particular to a device for generating or controlling process air which can be used, for example, for producing open hollow bodies, e.g. rotational bodies or cup-shaped molded parts (injection molded parts, also called injection moldings), such as bottle closures. According to the invention, the process air is used at two different pressures. For example, pre-air is first used at a first pressure to curve the base of the open hollow body molded parts (i.e. to shape the base), and for the subsequent ejection from the injection mold by means of discharge or discharge air.To blow out the molded parts for demolding, blowing air is used at a second pressure which has a different value than the first pressure.

[0005] BACKGROUND OF THE INVENTION

[0006] In recent years, plastic closures have become established in the beverage industry. These are primarily manufactured on injection molding machines. During production on the injection molding machine, these closures are ejected from the injection mold in free fall once dimensional stability has been achieved. Since the closures are mass-produced, not just one but several cavities are filled per production cycle, which can be arranged next to or on top of one another. Depending on the type of molded part or the closure principle, there are differences in the nature of the cavity and the type of ejection. At the beginning of the production of plastic closures, it was state of the art to turn the tool out of the closures. Since this takes up valuable cycle time, today the closures are forced demolded wherever geometrically possible.This means that they are pressed by the thread of the core, partly with mechanical and partly with pneumatic support.

[0007] The ejection process and the resulting drop pattern of the closures during ejection influence the process reliability and / or the cycle time of the injection molding machine, whereby both high process reliability and a short cycle time improve the yield and throughput of the injection molding process.

[0008] Compressed air is frequently used during the injection molding process for closures. On the one hand, the so-called pre-air is a process-related requirement during the demolding phase for releasing the closure from the core by arching the closure. For this purpose, compressed air is introduced between the closure and the core, in the parting line between the core face and the closure body remote from the thread, with the mold closed. This simplifies the removal of the closure from the core, as the resulting vacuum is overcome. Once the closure has then been mechanically removed from the core, in some cases the process air is used via the same air connection to distance the caps relative to the cavity, by briefly actuating the compressed air shortly after the ejection process. This helps ensure that the closures do not hit any mold parts and thus leave the injection mold safely in free fall towards the conveyor belt.However, the ejection process is primarily mechanical. The ejector is moved forward at the same speed as the mold closing. The movable side of the mold is then moved as quickly as possible toward the rear end position. This creates a drop pattern similar to that of a waterfall. In existing injection molding machines, the process air pressure is usually always the same, meaning the pre-air and blowing air have the same pressure.

[0009] It is state-of-the-art to eject the produced closures during the opening movement of the injection mold, thus saving valuable cycle time. The additional use of blow air helps to distance the closures from the injection mold, thus increasing process reliability.

[0010] The ejection process is time-critical. The desired, straight drop pattern is subject to various physical influences. The closures should always fall from the injection mold with the same drop pattern once the process has been set up. If this process is disrupted or subject to fluctuations, process reliability suffers. Such fluctuations in the blow air pressure can occur due to all kinds of actuators in the clamping unit, the ejector, or the blow air control system and can be of a physical or control-related nature. Fluctuations in the process air due to changing pressures and air flow times can lead to the closures no longer falling as desired. The way in which the closures fall can be influenced by the air pressure as well as the actuation time of the pneumatic valve. However, this blow molding process is subject to strict limitations.If the caps fall into the airflow of the next lower cavity, they spin, become swirled, or are blown too forcefully toward the nozzle-side injection mold half. Therefore, blow air is rarely used to blow off the caps. If the blow air control is too short, the cap will not be released. Variations in the air control and the resulting unpredictable behavior increase the likelihood of a process malfunction.

[0011] Because today the pneumatic valves used conventionally have two

[0012] Since processes have to be carried out with only one pressure, on the one hand as pre-air for curving the bottom of the closures and on the other hand as blowing air for ejection and spacing of the closures relative to the movable injection mold half, the requirements for the reproducibility of the pneumatic valves as well as all axes involved are very high.

[0013] There is therefore a need in the field of injection molding machines for (alternative) devices and processes which lead to improved (e.g. more reliable) or simpler demolding of molded parts than with the currently known means.

[0014] SUMMARY OF THE INVENTION

[0015] An object of the present invention is therefore to provide a device for providing process air for injection molding machines, with which improved demolding of the molded parts can be achieved. This object is achieved by the device specified in claim 1. With the aid of the invention, an injection molding machine can be equipped, which then implements the advantages of the invention in production. Such an injection molding machine is specified in claim 10. Furthermore, it is an object of the present invention to provide an improved method for demolding molded parts, which is achieved by the method defined in claim 13. Finally, a use of the device according to the invention is to be proposed. Such a use is specified in claim 17. Specific embodiments of the invention are listed in the respective dependent claims.

[0016] A device according to the invention for an injection molding machine with an injection mold, which serves to provide process air at a first and a comparatively different (i.e. higher or lower) second pressure, comprises a serial arrangement of two valves, wherein the first valve is connected on the one hand to a first pressure source with the first pressure and on the other hand to an (air) channel which leads into the injection mold, and the second valve is connected to a second pressure source with the second pressure and to a vent line, wherein the first and second valves are designed and controllable in such a way that the (air) channel can each be pressurized with either the first pressure or the second pressure.

[0017] The idea of ​​the invention and the difference between it and known solutions is the use of two different, (pre-)adjustable pressures (or pressure levels) using the same pneumatic connection between the valve plate and the injection mold. Although the injection mold has only one effective channel for introducing process air (e.g., on the one hand, for curving the molded parts and breaking the negative pressure / vacuum in the area between the molded parts and the surface of the injection mold using pre-air, and on the other hand, for blowing off the molded parts using blown air), which can of course also be present multiple times, the invention enables the production process with two separately (pre-)adjustable air supplies via a single valve.This has the advantage of extended adjustability, which increases the process window and reduces scatter because fluctuations in the actuators or machine control are less relevant in the case pattern, since the pressures for each process step (pre-air for curvature and blow air for ejection) can be set separately (in advance).

[0018] The device according to the invention comprises a chain or sequential connection (in series) of two independently switchable valves (valve I and valve II in Fig. 2), with valve I being connected downstream of the other valve II in such a way that, in its basic position, it supplies the injection mold with the pressure of valve II, provided the latter is actuated. This allows the injection mold to be supplied with different pressures via both the upstream and downstream valves, each with a different pressure supply. Both valves must never be actuated simultaneously, although this is never the case in the production process and is ensured by appropriate control of the two valves, especially since no high overpressure should be present in the cavity when the injection mold is opened.

[0019] In one design variant of the device, the two valves are 3 / 2-way valves, which have three connections and two switching positions. The 3 / 2-way valves each have a first connection for connection to a supply line, a second connection for connection to a working line, and a third connection for connection to a vent of the working line. In a first switching position, the first connection is closed and a passage from the second to the third connection is open, and in a second switching position, the third connection is closed and a passage from the first to the second connection is open. The first connection of the first valve is connected to the first pressure source, the second connection of the first valve is connected to the (air) channel, and the third connection of the first valve is connected to the second connection of the second valve.Furthermore, the first connection of the second valve is connected to the second pressure source and the third connection of the second valve is connected to the vent line for the discharge of (excess) process (exhaust) air.

[0020] In a further embodiment of the device, two or more serial arrangements of the two valves of a valve pair are connected in parallel, wherein each of the first valves of the valve pairs is connected to the first pressure source, and each of the second valves of the valve pairs is connected to the second pressure source and, in particular, to the vent line, and each of the first valves of the valve pairs is connected to the injection mold, in particular, via its own channel. Alternatively, each of the second valves of the valve pairs can be connected to its own vent line.

[0021] With such a parallel arrangement of several valve pairs, in a large injection mold in which a large number of molded parts are produced simultaneously, the process air can be introduced into the injection mold via several air ducts and the process exhaust air can then be discharged from the injection mold.

[0022] In a further embodiment of the device, (at least) one further valve is connected in series between the first valve and the second valve, wherein the further valve is connected to a further pressure source with a different pressure (i.e. higher or lower or intermediate) than the first and second. This valve can therefore take on further tasks. The first, second and further valves are designed and controllable in such a way that the (air) channel can each be pressurised with either the first, the second or the further pressure. The further valve can in particular be a 3 / 2-way valve. The first connection of the further valve is connected to the further pressure source, the second connection of the further valve is connected to the third connection of the first valve, and the third connection of the further valve is connected to the second connection of the second valve.

[0023] With such a chaining or sequential Z-series connection of three or more valves (beyond a valve pair to form a "valve tuple"), it is possible to provide the process air at even further pressure levels (3, 4, etc.) in order to realize correspondingly more complex (demoulding) processes.

[0024] In a further design variant of the device, the first pressure and / or the second pressure and / or the optionally further pressure(s) are adjustable. In this way, the pressures / pressure levels can be preset independently of one another according to requirements, whereby they are then kept essentially constant during operation of the injection molding machine. This means that the pressures / pressure levels are not changed during the process. By appropriately controlling the valves, it is possible to introduce the process air into the injection mold at a selected pressure (from the preset pressures of the various pressure sources). Switching between different pressures can therefore be carried out much more quickly and precisely than with a conventional system with only a single pressure source and an adjustable pressure control valve.

[0025] In a further embodiment of the device, the valves can be controlled electrically, in particular they are solenoid valves.

[0026] In a further embodiment, the device comprises a control unit which is designed to activate (open or close) only one of the first and second and optionally further valves in order to subject the channel to the first or second or optionally further pressure.

[0027] This allows the valves to be precisely controlled in the desired manner using an electrical / electronic control unit, and allows complex processes (with multiple valves) to be flexibly programmed and monitored. This, in particular, prevents undesirable situations, thereby increasing process reliability.

[0028] The invention extends the possibility of influencing the process in additional respects, e.g. by connecting other components, as listed below.

[0029] In a further embodiment, the device further comprises a compressed air reservoir which is connected to the first or second pressure source and the first or second valve, in particular the first connection of the first or second valve.

[0030] The blowing air tract can be supported by this compressed air reservoir. This reduces a significant pressure drop during valve actuation (see Fig. 2, Valve I) and stabilizes the air flow by decoupling the supply line. In a further embodiment, the device further comprises a check valve arranged in the vent line, in particular further comprising a silencer arranged in the vent line, wherein the check valve is arranged between the second valve and the silencer, wherein, in particular, a preload of the check valve is adjustable.

[0031] The venting of the pneumatic circuitry typically has a silencer. It is possible to install a check valve at this point. This would result in a spring pressure equivalent to the check valve being applied, even when the pre-air valve (see Fig. 2, Valve II, Port 3) is deactivated. This reduces air consumption and prevents the air channel in the injection mold from being completely emptied via the venting. The subsequent ejection process is thus somewhat more defined, as less air is required to build up pressure.

[0032] As a further aspect of the present invention, an injection molding machine comprising an injection mold and a device as specified above is proposed. The device is connected to the injection mold via one or more (air) channels in order to introduce process air into the injection mold at at least two different pressures.

[0033] In one embodiment, the injection molding machine further comprises one or more mechanical ejectors, for example in the form of a scraper ring, to support a demolding process of the molded parts, which is designed to detach molded parts from the injection mold or from a surface of the injection mold and / or to eject molded parts from the injection mold.

[0034] In one embodiment, the injection molding machine is designed to produce open hollow bodies, such as rotary bodies or cup-shaped molded parts, in particular to produce a plurality of such molded parts simultaneously, wherein the injection molding tool in particular has a plurality of cavities, which are arranged in columns next to one another or in rows one above the other, for forming the molded parts.

[0035] As a further aspect of the present invention, a method for demolding molded parts, in particular open hollow bodies such as rotary bodies or cup-shaped molded parts, for example bottle closures, from an injection mold in an injection molding machine as specified above using a device as specified above is proposed. Such a method according to the invention comprises the following steps following an injection molding process, in particular during a cooling phase of the molded parts in the injection mold of the injection molding machine:

[0036] □ Applying a pre-air pressure to the channel by opening a passage in a pre-air valve which connects the pre-air source to the channel, and by (previously) closing a passage in a blow air valve which connects a blow air pressure source to the channel, in particular in order to introduce pre-air with the pre-air pressure into the injection mold, in particular between the respective molded part and a core of the injection mold when the injection mold is closed, in particular in order to arch the respective molded part, in particular in order to break a vacuum between the respective molded part and the core in order to separate the molded parts from the injection mold;

[0037] □ (subsequently) applying a blowing air pressure to the channel by opening a passage in the blowing air valve, which connects the blowing air pressure source to the channel, and by (previously) closing a passage in the pre-air valve, which connects the pre-air pressure source to the channel, in particular in order to introduce blowing air with the blowing air pressure into the injection mold, in particular into an interior of the open hollow molded parts, such as rotary bodies or cup-shaped molded parts, in order to blow the molded parts out of the injection mold;

[0038] □ Vent the injection mold by closing the passage in the blow air valve, which connects the blow air pressure source to the channel, and by opening the respective passages in the pre-air and blow air valve, which connects the channel to the vent line.

[0039] The pre-air pressure can be either the second or first pressure in the device, and the blowing air pressure can be either the first or second pressure in the device. Thus, the pre-air source can be either the second or first pressure source in the device, and the blowing air source can be either the first or second pressure source in the device. The pre-air valve can be either the second or first valve in the device, and the blowing air valve can be either the first or second valve in the device.

[0040] In one embodiment, the method comprises at least one of the following two additional steps:

[0041] □ Actuating a mechanical ejector to assist the demoulding process, in particular during or after the channel is subjected to pre-air pressure in order to detach moulded parts from the injection mould or from a surface of the injection mould;

[0042] □ Actuating a mechanical ejector to assist the demoulding process, particularly before or during the application of blow air pressure to the channel in order to eject moulded parts from the injection mould.

[0043] In a further embodiment, the method also includes the following additional step:

[0044] □ Supporting the blowing air pressure via a compressed air reservoir in order to reduce a strong pressure drop during actuation of the blowing air valve and to stabilize an air flow by decoupling a feeding blowing air line (from the blowing air source to the blowing air valve).

[0045] In a further embodiment, the method also comprises the following additional step: □ Generating an (adjustable) spring pressure in the vent line by means of a check valve when switching off the pre-air valve in order to reduce the consumption of process air and to prevent a complete emptying of the channel (to and in particular in the injection mold) via the vent line.

[0046] It should be expressly noted that combinations of the embodiments listed above may form further embodiments of the invention (provided they do not contradict each other).

[0047] As a further aspect of the present invention, a use of the above-mentioned device (for providing process air) for demoulding moulded parts, in particular open hollow bodies, such as rotary bodies or cup-shaped moulded parts, e.g. bottle closures, from an injection moulding tool during production by means of an injection moulding machine is proposed.

[0048] BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Non-limiting embodiments of the present invention are explained in more detail below with reference to the figures. They show:

[0050] Fig. 1 is a schematic representation (in the form of a pneumatic circuit or circuit diagram) of a device according to the prior art for providing process air for demoulding moulded parts in an injection moulding machine; and

[0051] Fig. 2 is a schematic representation (in the form of a pneumatic circuit or circuit diagram) of a device according to the invention for providing process air for demolding molded parts in an injection molding machine (with several optional features).

[0052] In the figures, like reference numerals represent like elements. DETAILED DESCRIPTION OF THE INVENTION

[0053] Fig. 1 shows a schematic representation (in the form of a pneumatic circuit or a pneumatic circuit diagram) of a known device for providing process air for demolding molded parts in an injection molding machine. Here, the process air is supplied from a single compressed air source p at a constant pressure. Based on this fixed output pressure of the compressed air source p, the pressure of the process air is adjusted (e.g. reduced) during the demolding process by means of the (proportional) pressure control valve 15 according to the current requirements. The process air is then introduced into the injection mold 10 via the single valve I and the (branched) channel 11 (via two process air inlets E1, E2). For this purpose, the valve I is electrically actuated by a control system, so that the passage through the valve I from connection 1 to connection 2 is opened for the process air.During the demolding process, the pressure of the process air is reduced, for example by means of the pressure control valve 15, during the transition from pre-air for detaching the molded parts from the surface of the injection mold 10 to blowing air for ejecting the molded parts from the injection mold 10, whereby the passage through valve 1 from port 1 to port 2 remains open. The pressure change through the pressure control valve 15 occurs relatively slowly so that, for example, no rapid pressure drops can occur. During the venting phase, the passage from port 1 to port 2 is closed and instead the passage from port 2 to port 3 is opened in order to discharge the process exhaust air through the vent line 12. It is guided over a silencer 13 to reduce loud noises.Since the process air is switched by a single valve I, it may be necessary for the channel 11 for supplying process air to the injection mold 10 to branch off into multiple connections (in Fig. 1, the air inlets E1 & E2) on the injection mold 10 (in Fig. 1, there are two branches). With this known device, fluctuations in the process air due to changing pressures and flow times of the air, caused by the pneumatic path with the pressure control valve, can lead to the molded parts not being ejected from the injection mold 10 as desired and therefore falling out differently. In addition, suitable (proportional) pressure control valves are expensive, require a variable control signal, and are less reliable than simple valves that can only be opened or closed.

[0054] In order to eliminate these disadvantages and to eliminate or at least improve the variations in the air control (regarding the pressure of the process air and the actuation times of the pneumatic valve) and the associated unpredictable behavior in order to avoid process disturbances, embodiment variants of the device according to the invention for providing process air at different pressures for more reliable demolding in injection molding machines are described below.

[0055] Thus, Fig. 2 shows a schematic representation (in the form of a pneumatic circuit or a pneumatic circuit diagram) of a device 100 according to the invention for providing process air for demolding molded parts in an injection molding machine (with several optional features). The device 100 comprises two valve pairs 1a, Ha and 1b, Hb, one of these two valve pairs being optional. The core of the invention is the serial arrangement shown in Fig. 2 and the corresponding pairwise interconnection of two valves each, each valve 1a, Ha (or 1b, Hb) of the valve pair being connected to its own compressed air source (or process air source) pl, pH. The pressures of the two compressed air sources pl and pH are different and are preset (i.e. before the start of the process) and then kept fixed (i.e. essentially constant).For example, the blowing air pressure of the blowing air source pl for blowing the molded parts out of the injection mold is (significantly) lower than the pre-air pressure of the pre-air source pH for arching the molded parts, with which the vacuum between the core of the injection mold and the molded parts is broken and the molded parts are released from the surface of the injection mold. It should be noted at this point that the release process (as well as the ejection) is usually supported by mechanical ejectors, with the blowing essentially serving to achieve the desired distance between the molded parts and the injection mold, whereupon the molded parts then fall safely out of the injection mold without touching it anywhere else. The correct setting and maintenance of the blowing air pressure is particularly important for injection molds that have a large number of cavities arranged in rows one above the other (or one above the other) for the simultaneous molding of many molded parts.In this case, it is important that the blowing air from the lower cavities does not touch the falling parts from higher cavities and, for example, pushes them against the opposite side of the injection mold. For certain applications, however, it is also conceivable to set the blowing air pressure (in advance) higher than the pre-air pressure.

[0056] In Fig. 2, the pressure source pH connected to the lower valve Ha is the pre-air source (for providing the pre-air pressure) and the pressure source pl connected to the upper valve la is the blast air source (for providing the blast air pressure). Accordingly, we refer to the lower valve Ha as the pre-air valve and the upper valve la as the blast air valve. However, the upper pressure source pl could also be the pre-air source and the lower pressure source pH the blast air source. Accordingly, the upper valve la would then be the pre-air valve and the lower valve Ha the blast air valve. It is typically advantageous if the blast air valve la is connected downstream of the pre-air valve Ha, as shown in Fig. 2, since the pre-air pressure is usually (much) higher than the blast air pressure and a certain pressure drop occurs when the process air flows through each valve.Since the pre-air flow through the two valves 1a and 1a is very low, the pressure drop is also very small. The blown air only flows through the blown air valve, so the pressure drop is also very small.

[0057] The two valves are fundamentally identical, except that the upper valve 1a is directly connected to the air duct 11a, which carries the process air to the injection mold 10, while the lower valve Ha can be connected indirectly to the air duct 11a via the upper valve 1a. Conversely, the lower valve Ha is directly connected to the vent line 12, whereas the upper valve 1a can be connected indirectly to the vent line 12 via the lower valve Ha. Bistable valves should be used preferably. From a signaling perspective, the valves used are usually monostable, but electro-pneumatically pilot-controlled, with the main spool of the respective valve being pushed into a defined end position, whereby the valves act bistable. This guarantees that the pre-air from the pre-air valve flows reliably through the blast air valve.

[0058] Both valves la, Ha are typically designed as 3 / 2-way valves, which have a first connection 1 for connection to a supply line (to the pressure source pl, pH), a second connection 2 for connection to a working line (to the injection mold 10) and a third connection 3 for connection to a vent of the working line (to the vent line 12).

[0059] For the demolding of molded parts from the injection mold 10 according to the invention following the injection molding process and in particular during the cooling phase of the molded parts, the following process steps are carried out. First, the air channel 11a is pressurized with the pre-air pressure from the pre-air source pH. For this purpose, the passage from port 1 to port 2 in the pre-air valve Ha must be opened, and in addition, the passage from port 3 to port 2 in the downstream blow-air valve 1a must also be opened. If both valves are electrically controllable, so-called "normally closed" (i.e., closed in the basic position - as shown in Fig. 2) or so-called "normally open" (i.e.,in the basic position open) valves, the valve control will have to control the (lower) pre-air valve Ha in the opposite way to the (upper) blow-air valve la, because with the blow-air valve la the passage from connection 1 to 2 must be closed if the passage from connection 3 to 2 is open, and with the pre-air valve Ha the passage from connection 1 to 2 must be open if the passage from connection 3 to 2 is closed. By closing the passage from connection 1 to 2 in the blow-air valve la, the blow-air source pl is not connected to the channel 11a and thus not to the injection mold 10. On the other hand, by opening the passage from connection 1 to 2 in the pre-air valve Ha, the pre-air source pH is indirectly connected to the air channel 11a and thus to the injection mold 10 via the open passage from connection 3 to 2 in the blow-air valve la, so that the pre-air pressure is applied there.By introducing the pre-air at the pre-air pressure into the injection mold 10, which takes place between the molded parts and the corresponding cores of the injection mold 10 when the injection mold 10 is closed, the molded parts bulge (in particular the bottoms of open hollow bodies, such as rotational bodies or cup-shaped molded parts) and a vacuum or negative pressure between the respective molded part and the core is broken, so that the molded parts are released from the injection mold 10 after a certain period of pre-air supply.

[0060] As soon as the desired duration of the pre-air supply has elapsed, the passage from connection 1 to 2 at the pre-air valve Ha is closed again by means of appropriate control of the pre-air valve Ha, so that the pre-air source pH is separated from channel 11a. By closing the passage from connection 1 to 2 at the pre-air valve Ha, the passage from connection 2 to 3 at the pre-air valve Ha is (automatically) opened, which leads to the venting of the process exhaust air from the injection mold 10 via the air channel 11a and the open passage from connection 2 to 3 at the blow-air valve 1a into the vent line 12.

[0061] Subsequently, the air duct 11a is pressurized with the blowing air pressure from the blowing air source pl. For this purpose, the passage from port 1 to port 2 in the blowing air valve 1a must be opened, while the passage from port 1 to port 2 at the upstream pre-air valve Ha is closed (which is the case when port 2 to port 3 at the pre-air valve Ha is open) in order to connect the blowing air source pl with the blowing air pressure to the injection mold 10, to introduce blowing air into it (in particular into the interior of molded parts with an open hollow body), to blow the molded parts out of the injection mold 10, or to distance the molded parts from the injection mold 10 (typically supported or even primarily caused by mechanical ejectors).

[0062] After the molded parts have been blown out by the blow air supply for a desired period of time, the passage from connection 1 to 2 at the blow air valve la is closed again by appropriately controlling the blow air valve la, so that the blow air source pl is separated from the channel 11a. By closing the passage from connection 1 to 2 at the blow air valve la, the passage from connection 2 to 3 at the blow air valve la is (automatically) opened, which leads to the venting of the process exhaust air from the injection mold 10 via the air channel 11a and the open passage from connection 2 to 3 at the pre-air valve Ha into the vent line 12.

[0063] In this case, both the detachment of the molded parts from the surface of the injection mold 10 and the blowing or ejection of the molded parts from the injection mold 10 can be additionally supported by actuating a mechanical ejector (either both or only one of detachment and blowing / ejection).

[0064] Furthermore, a compressed air reservoir 16 can be used to support the blowing air pressure. This reservoir is connected to the blowing air supply line from the blowing air source pl to connection 1 of the blowing air valve 1a. This reduces a significant pressure drop during actuation of the blowing air valve 1a and stabilizes the air flow by decoupling the supplying blowing air supply line.

[0065] Furthermore, by means of a check valve 17, an (adjustable) spring pressure can be generated in the vent line 12 when the pre-air valve Ha is switched off, which leads to a reduction in the consumption of process air and prevents the air duct 11a from being completely emptied via the vent line 12. In addition, the set pre-tension pressure on the check valve 17 can (intentionally) extend the duration of the detachment process, even if the pre-air valve Ha has already been closed. In the case of a large injection mold 10, for example in order to be able to simultaneously produce a large number of open hollow bodies, such as rotary bodies or cup-shaped molded parts, e.g. closure caps, with a large number of cavities, which are arranged, for example, in columns next to one another or in rows one above the other, several air ducts 11a, 11b may be required to introduce process air into the injection mold 10.Instead of branching just one air duct (multiple times) and leading it to multiple connections E1, E2 on the injection mold 10, it can be advantageous to use multiple separate air ducts 11a, 11b in order to improve the process air supply. Each air duct 11a, 11b can be assigned its own valve pair 1a+11a, 11b, as shown in Fig. 2. A first valve pair consisting of the blow air valve 1a and the upstream pre-air valve Ha operates the first air duct 11a. A second, parallel valve pair consisting of the blow air valve 1b and the upstream pre-air valve Hb operates the second air duct 11b. The two pre-air valves Ha, Hb are connected to the common pre-air source pH, while the two blow air valves 1a, 1b are connected to the common blow air source pl.Both air ducts 11a, 11b are vented via a common vent line 12, although this could also be done via two separate vent lines. The two valve pairs 1a+11a and 1b+11b are controlled identically, although the switching operations must be fine-tuned depending on the size of the injection mold 10 in order to achieve the desired demolding sequence. For example, in a large injection mold with ten process air connections, ten parallel valve pairs can be used to optimize the process air supply. It should also be noted that smaller valves are more cost-effective and more dynamic (faster).

[0066] Furthermore, it is also possible to insert another valve between the first and the upstream second valve of a serially arranged valve pair to connect a third process air source delivering a different pressure. In this way, additional (4th, 5th, etc.) process air sources could also be connected and used in the demolding process.

[0067] List of reference symbols

[0068] 1 first valve connection for supply line

[0069] 2 second valve connection for working line

[0070] 3 third valve connection for venting (of the working line)

[0071] 10 injection mold

[0072] 11 (Air) channel from the valve to the injection mold (with two air inlets into the injection mold)

[0073] 11a (Air) channel from valve la to the injection mold (with a first air inlet into the injection mold)

[0074] 11 b (Air) channel from valve Ib to the injection mold (with a second air inlet into the injection mold)

[0075] 12 Ventilation (line)

[0076] 13 silencers

[0077] 14 Electrical control of the valve

[0078] 15 adjustable pressure control valve

[0079] 16 compressed air storage tanks

[0080] 17 Check valve (spring-loaded, e.g. with adjustable preload)

[0081] 100 Device for providing process air

[0082] E1 , E2 Air inlet into the injection mold

[0083] Ea, Eb Air inlet into the injection mold

[0084] I Valve, 3 / 2-way valve (with electrical actuation) for pre-air and blown air la first valve of the valve pair a, 3 / 2-way valve (with electrical actuation) for blown air

[0085] Ha second valve of valve pair a, 3 / 2-way valve (with electrical actuation) for pre-air

[0086] Ib first valve of valve pair b, 3 / 2-way valve (with electrical actuation) for blown air

[0087] Hb second valve of valve pair b, 3 / 2-way valve (with electrical actuation) for pre-air p pressure (air) source with fixed (air) pressure pl pressure (air) source with first fixed (air) pressure pH pressure (air) source with second fixed (air) pressure + first (air) pressure

Claims

Claims 1. Device (100) for an injection molding machine with an injection mold (10) for providing process air at a first and a second pressure which is different in comparison thereto, characterized in that the device (100) has a serial arrangement of two valves (1a, Ha; Ib, Hb), the first valve (1a; Ib) being connected on the one hand to a first pressure source (p1) having the first pressure and on the other hand to a channel (11a; 11b) which leads into the injection mold (10), and the second valve (Ha; Hb) being connected to a second pressure source (pH) having the second pressure and to a vent line (12), the first and second valves (1a, Ha; Ib, Hb) being designed and controllable in such a way that the channel (11a; 11b) can each be subjected to either the first or the second pressure.

2. Device (100) according to claim 1, characterized in that the two valves (1a, Ha; Ib, Hb) are 3 / 2-way valves, each having a first connection (1) for connection to a supply line, a second connection (2) for connection to a working line and a third connection (3) for connection to a vent of the working line, wherein the first connection (1) of the first valve (1a, Ib) is connected to the first pressure source (p1), the second connection (2) of the first valve (1a; Ib) is connected to the channel (11a; 11b), and the third connection (3) of the first valve (1a; Ib) is connected to the second connection (2) of the second valve (Ha; Hb), and wherein the first connection (1) of the second valve (Ha; Hb) is connected to the second pressure source (pH), and the third connection (3) of the second valve (Ha; Hb) is connected to the vent line (12) for the discharge of process air.

3. Device (100) according to one of claims 1 or 2, characterized in that two or more serial arrangements of the two valves (la, Ha; Ib, Hb) of a valve pair are connected in parallel, wherein each of the first valves (la; Ib) of the valve pairs is connected to the first pressure source (pl), and each of the second valves (Ha; Hb) of the valve pairs is connected to the second pressure source (pH) and in particular to the vent line (12), and each of the first valves (la; Ib) of the valve pairs is connected to the injection molding tool (10) in particular via its own channel (11a; 11b).

4. Device (100) according to one of claims 1 to 3, characterized in that a further valve is connected in series between the first valve (1a; 1b) and the second valve (Ha; Hb), wherein the further valve is connected to a further pressure source with a different further pressure than the first and second, wherein the first (1a; 1b), second (Ha; Hb) and further valve are designed and controllable in such a way that the channel (11a; 11b) can each be subjected to either the first, the second or the further pressure, wherein the further valve is in particular a 3 / 2-way valve, wherein in particular the first connection of the further valve is connected to the further pressure source, the second connection of the further valve is connected to the third connection (3) of the first valve (1a; 1b), and the third connection of the further valve is connected to the second connection (2) of the second valve (Ha; Hb).

5. Device (100) according to one of claims 1 to 4, characterized in that the first pressure and / or the second pressure and / or the optionally further pressure is adjustable.

6. Device (100) according to one of claims 1 to 5, characterized in that the valves (la, Ha; Ib, Hb) are electrically controllable, in particular that the valves (la, Ha; Ib, Hb) are solenoid valves.

7. Device (100) according to one of claims 1 to 6, further comprising a control unit which is designed to activate only one of the first and second and optionally further valves (1a, Ha; 1b, Hb) in order to apply the first or second or optionally further pressure to the channel (11a; 11b).

8. Device (100) according to one of claims 1 to 7, further comprising a compressed air reservoir (16) which is connected to the first or second pressure source (pl, pH) and the first or second valve (la, Ha; Ib, Hb), in particular the first connection (1 ) of the first or second valve (la, Ha; Ib, Hb).

9. Device (100) according to one of claims 1 to 8, further comprising a check valve (17) which is arranged in the vent line (12), in particular further comprising a silencer which is arranged in the vent line (12), wherein the check valve (17) is arranged between the second valve (Ha; Hb) and the silencer, wherein in particular a preload of the check valve (17) is adjustable.

10. Injection molding machine with an injection mold (10) and a device (100) according to one of claims 1 to 9, wherein the device (100) is connected to the injection mold (100) via one or more channels (11 a, 11 b) in order to be able to introduce process air into the injection mold (10) at at least two different pressures.

11. Injection molding machine according to claim 10, further comprising one or more mechanical ejectors, for example in the form of a scraper ring, which is designed to detach molded parts from the injection mold (10) or from a surface of the injection mold (10) and / or to eject molded parts from the injection mold, in order to support a demolding process of the molded parts.

12. Injection molding machine according to claim 10 or 11, which is designed to produce open hollow bodies, such as rotary bodies or cup-shaped molded parts, in particular to produce a plurality of such molded parts simultaneously, wherein the injection molding tool (10) has in particular a plurality of cavities, which are arranged in columns next to one another or in rows one above the other, for forming the molded parts.

13. A method for demoulding moulded parts, in particular open hollow bodies, such as rotary bodies or cup-shaped moulded parts, for example bottle closures, from an injection moulding tool (10) in an injection moulding machine according to one of claims 10 to 12 by means of a device (100) according to one of claims 1 to 9, comprising the following steps following an injection moulding process, in particular during a cooling phase of the moulded parts in the injection moulding tool (10) of the injection moulding machine: Applying a pre-air pressure to the channel (11a; 11b) by opening a passage in a pre-air valve which connects the pre-air source to the channel (11a; 11b), and by closing a passage in a blowing air valve which connects a blowing air pressure source to the channel (11a; 11b), in particular in order to introduce pre-air with the pre-air pressure into the injection molding tool (10), in particular between the respective molded part and a core of the injection molding tool (10) when the injection molding tool (10) is closed, in particular in order to arch the respective molded part, in particular in order to break a vacuum between the respective molded part and the core in order to thus separate the molded parts from the injection molding tool (10); Applying a blowing air pressure to the channel (11a; 11b) by opening a passage in the blowing air valve, which connects the blowing air pressure source to the channel (11a; 11b), and by closing a passage in the pre-air valve, which connects the pre-air pressure source to the channel (11a; 11b), in particular in order to introduce blowing air with the blowing air pressure into the injection molding tool (10), in particular into an interior of the open hollow bodies, such as rotary bodies or cup-shaped molded parts, in order to blow the molded parts out of the injection molding tool (10); Venting the injection mold (10) by closing the passage in the blowing air valve, which connects the blowing air pressure source to the channel (11a; 11b), and by opening the respective passages in the pre-air and blowing air valve, which connect the channel (11a; 11b) to the vent line (12), wherein the pre-air pressure is either the second or first pressure in the device (100) and the blowing air pressure, conversely, is either the first or second pressure in the device (100), and thus the pre-air source is either the second or first pressure source (pH, pI) in the device (100) and the blowing air source, conversely, is either the first or second pressure source (pI, pH) in the device (100), and wherein the pre-air valve is either the second or first valve (Ha, Ia; Hb, Ib) in the device (100) and the blowing air valve, conversely, is either the first or second valve (la, Ha; Ib, Hb) in the device (100).

14. Method according to claim 13 carried out with the injection molding machine according to claim 11, with at least one of the following two additional steps: Actuating a mechanical ejector to assist the demoulding process, in particular during or after the channel (11a; 11b) is subjected to the pre-air pressure, in order to detach moulded parts from the injection moulding tool (10) or from a surface of the injection moulding tool (10); Actuating a mechanical ejector to assist the demoulding process, in particular before or during the application of the blowing air pressure to the channel (11a; 11b) in order to eject moulded parts from the injection moulding tool (10).

15. The method according to claim 13 or 14, comprising the following additional step: supporting the blowing air pressure via a compressed air reservoir (16) in order to reduce a strong pressure drop during actuation of the blowing air valve and to stabilize an air flow by decoupling a feeding blowing air line.

16. A method according to any one of claims 13 to 15, comprising the following additional step: Generating a spring pressure in the vent line (12) by means of a check valve (17) when switching off the pre-air valve in order to reduce consumption of process air and to prevent complete emptying of the channel (11a; 11b) via the vent line (12).

17. Use of the device (100) according to one of claims 1 to 9 for demoulding moulded parts, in particular open hollow bodies, such as rotary bodies or cup-shaped moulded parts, e.g. bottle closures, from an injection moulding tool (10) during production by means of an injection moulding machine.

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