WO2024074259A1 - Device for producing process air and method for demoulding moulded parts for injection-moulding machines - Google Patents

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

Description

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

TECHNICAL FIELD OF THE INVENTION

The invention relates to a fluid power device for applications on injection molding machines which require process air and which have high requirements for the reproducibility of demolding. This is particularly the case in the manufacture 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, to manufacture open hollow bodies, e.g. rotating bodies or cup-shaped molded parts (injection molded parts, also called injection moldings), such as bottle caps. 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 blowing air is used at a second pressure, which has a different value than the first pressure, for the subsequent ejection process from the injection mold by blowing off or out the molded parts for demolding.

BACKGROUND OF THE INVENTION

In recent years, plastic closures have become popular in the beverage industry. These are mainly manufactured on injection molding machines. During production on the injection molding machine, these closures are ejected from the injection molding tool in free fall after they have achieved dimensional stability. Since the closures are manufactured in mass production, Not just one but several cavities are filled per production cycle, which are arranged either next to or on top of each other. 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, the state of the art was to unscrew the tool from the closures. Since this takes up valuable cycle time, today the closures are forcibly demolded wherever geometrically possible. This means that they are pressed from the thread of the core, partly with mechanical and partly with pneumatic support.

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.

Compressed air is often used during the injection molding process for the closures. On the one hand, the so-called pre-air during the demolding phase is a process-technical requirement for the ventilation of 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 plane between the core face and the closure body remote from the thread when the tool is closed. This makes it easier to separate the closure from the core because the vacuum that has arisen is overcome. Once the closure has been mechanically separated from the core, in individual cases the process air is used via the same air connection to distance the caps relative to the cavity by briefly activating the compressed air shortly after the ejection process. This helps to ensure that the closures do not hit tool parts and thus leave the injection mold safely in free fall towards the conveyor belt. The main ejection, however, takes place mechanically. The ejector is moved forward at the same speed as the mold closure. The movable side of the tool is then moved away as quickly as possible towards the rear end position. This creates a case pattern similar to the a waterfall. In existing injection molding machines, the pressure of the process air is usually always the same, ie the pre-air and the blowing air have the same pressure.

It is state of the art that the closures produced are ejected during the opening movement of the injection mold, thus saving valuable cycle time. The additional use of blowing air helps to distance the closures from the injection mold and thus increases process reliability.

The ejection process is time-critical. The desired, straight-line drop pattern is subject to various physical factors. The caps should always fall out of the injection mold with the same drop pattern if possible once the process has been set up. If this process is disrupted or subject to fluctuations, process reliability suffers. Such fluctuations in the pressure of the blowing air can occur due to all types of actuators in the clamping unit, in the ejector or in the blowing air control and can be of a physical or control-technical nature. Fluctuations in the process air due to changing pressures and flow times of the air can lead to the caps no longer falling as desired. The way in which the caps fall can be influenced by the air pressure as well as the control time of the pneumatic valve. However, this blowing process is subject to strict limits. If the caps fall into the air flow of the next cavity below, they rotate, become swirled or are blown too strongly in the direction of the nozzle-side half of the injection mold. This is why blowing air is rarely used to blow off the caps. If the blowing air is controlled for too short a time, the shutter will not be released. Variations in the air control and the resulting unpredictable behavior increase the likelihood of a process malfunction.

Because today the pneumatic valves used conventionally have two

Processes must be carried out with only one pressure, on the one hand as pre-air for On the one hand, the curvature of the bottom of the closures and, on the other hand, the blowing air for ejection and spacing of the closures relative to the movable injection mold half mean that the requirements for the reproducibility of the pneumatic valves as well as all axes involved are very high.

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.

SUMMARY OF THE INVENTION

One 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 help 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.

A device according to the invention for an injection molding machine with an injection molding tool, which serves to provide process air at a first and a comparatively different (ie 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 molding tool, and the second valve is connected to a second pressure source with the second pressure and a vent line, wherein the first and second valves are designed and controllable such that the (air) channel can each be subjected to either the first pressure or the second pressure.

The idea of the invention and the difference of the invention compared to 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 to curve the molded parts and to break 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 to blow off the molded parts using blowing 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 valve. This has the advantage of extended adjustability, which increases the process window and reduces scatter, because in the case scenario fluctuations in the actuators or machine control are less relevant, since the pressures for each process step (pre-air for curve and blowing air for ejection) can be set separately (in advance).

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 molding tool with the pressure of valve II, provided that the latter is actuated. This means that the injection molding tool can be supplied with different pressures via both the upstream and downstream valves. Both valves must never be actuated at the same time, which is never the case in the production process and can be prevented by a corresponding Control of the two valves is ensured, especially since there should not be a high overpressure in the cavity when the injection molding tool is opened.

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 discharging (excess) process (exhaust) air.

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 molding tool in particular via its own channel. Alternatively, each of the second valves of the valve pairs can be connected to its own vent line.

With such a parallel arrangement of several valve pairs, in a large injection mold in which a large number of molded parts are manufactured simultaneously, the process air can be fed into the injection mold via several air ducts. injection molding tool and the process exhaust air is then discharged from the injection molding tool.

In a further embodiment of the device, (at least) one further valve is connected in series between the first valve and the second valve, the further valve being 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 pressurized with either the first, second or 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.

With such a chain connection 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 higher pressure levels (3, 4, etc.) in order to be able to realize correspondingly more complex (demoulding) processes.

In a further variant of the device, the first pressure and/or the second pressure and/or the additional pressure(s) can be set. The pressures/pressure levels can be preset independently of one another to suit the requirements, and 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 controlling the valves accordingly, it is possible to introduce the process air into the injection molding tool at a selected pressure (from the preset pressures of the various pressure sources). Switching between different pressures can thus be done much more quickly and more precise than with a conventional system with only one pressure source and an adjustable pressure control valve.

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

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.

This means that the valves can be controlled precisely in the desired manner using an electrical/electronic control unit, and complex processes (with many valves) can be programmed and monitored flexibly, for example. This can prevent undesirable situations in particular, thereby increasing process reliability.

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

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.

The blowing air tract can be supported by this compressed air reservoir. This reduces a strong pressure drop during valve operation (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 which is arranged in the vent line, in particular further comprising a silencer which is 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.

The venting of the pneumatic circuit usually has a silencer. It is possible to install a check valve at this point. This would result in a spring pressure corresponding to the check valve being applied despite the pre-air valve being switched off (see Fig. 2 valve II, connection 3). 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 needed to build up the pressure.

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

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 molding tool or from a surface of the injection molding tool and/or to eject molded parts from the injection molding tool.

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 large number of such molded parts simultaneously, whereby 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.

As a further aspect of the present invention, a method is proposed 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 molding tool in an injection molding machine as specified above by means of a device as specified above. 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 molding tool of the injection molding machine:

□ 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 blowing air valve which connects a blowing air pressure source to the channel, in particular to introduce pre-air with the pre-air pressure into the injection molding tool, in particular between the respective molded part and a core of the injection molding tool when the injection molding tool is closed, in particular to arch the respective molded part, in particular to break a vacuum between the respective molded part and the core in order to separate the molded parts from the injection molding tool;

□ (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 body molded parts, such as rotary bodies or cup-shaped molded parts, in order to blow the molded parts out of the injection mold;

□ Venting 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 duct with the vent line.

The pre-air pressure can be either the second or first pressure in the device and the blowing air pressure can conversely 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 conversely 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 conversely be either the first or second valve in the device.

In one embodiment, the method comprises 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 is subjected to pre-air pressure in order to detach moulded parts from the injection moulding tool or from a surface of the injection moulding tool;

□ Operating a mechanical ejector to assist the demoulding process, particularly before or during the application of blowing air pressure to the channel in order to eject moulded parts from the injection moulding tool.

In a further embodiment, the method also comprises the following additional step:

□ Supporting the blowing air pressure via a compressed air reservoir to reduce a strong pressure drop during operation of the blowing air valve and to stabilize an air flow by decoupling a supply blowing air line (from the blowing air source to the blowing air valve).

In a further embodiment, the method also comprises the following additional step: □ Generation of 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 consumption of process air and to prevent complete emptying of the channel (to and especially in the injection molding tool) via the vent line.

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

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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).

In the figures, the same reference symbols refer to the same elements. DETAILED DESCRIPTION OF THE INVENTION

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) in the course of the demolding process by means of the (proportional) pressure control valve 15 according to the current requirements, which 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 operated 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 during the transition from preliminary 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, for example by means of the pressure control valve 15, whereby the passage through the valve I from connection 1 to connection 2 remains open. The pressure change through the pressure control valve 15 takes place relatively slowly so that, for example, no rapid pressure drops can be achieved. During the venting phase, the passage from connection 1 to connection 2 is closed and instead the passage from connection 2 to connection 3 is opened in order to discharge the process exhaust air through the venting line 12. It is guided via a silencer 13 in order 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 molding tool 10 to branch into several connections (in Fig. 1 the air inlets E1 & E2) at the injection molding tool 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.

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 control times of the pneumatic valve) and the associated unpredictable behavior in order to avoid process disturbances, design 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.

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 la, Ha and Ib, 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 connection of two valves each, each valve la, Ha (or Ib, 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 detached from the surface of the injection mold. It should be noted at this point that the detachment process (as well as the ejection) usually is also supported by mechanical ejectors, whereby the blowing essentially serves 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. 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 in columns next to each other) for the simultaneous molding of many molded parts. In this case, it is important that blowing air from the lower cavities does not affect the molded parts falling down from higher cavities and, for example, presses them against the opposite side of the injection mold. For certain applications, however, it is also conceivable that the blowing air pressure is (in advance) set higher than the pre-air pressure.

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

The two valves are basically identical, except that the upper valve la is directly connected to the air channel 11a, which leads the process air to the injection molding tool 10, while the lower valve Ha can be connected indirectly to the air channel 11a via the upper valve la. Conversely, the lower valve Ha is directly connected to the The valves are connected to the vent line 12, whereas the upper valve la can be connected indirectly to the vent line 12 via the lower valve Ha. Bistable valves should preferably be used. The valves used are usually monostable in terms of signal technology, but are electro-pneumatically pilot-controlled, which pushes the main slide of the respective valve into a defined end position, causing the valves to act bistable. This guarantees that the pre-air from the pre-air valve flows through the blow air valve in a process-safe manner.

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).

For the inventive demolding of molded parts from the injection molding tool 10 following the injection 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 subjected to the pre-air pressure from the pre-air source pH. To do this, the passage from connection 1 to connection 2 in the pre-air valve Ha must be opened, and in addition the passage from connection 3 to connection 2 in the downstream blowing air valve la must also be opened. If both valves are electrically controllable so-called "normally closed" (ie closed in the basic position - as shown in Fig. 2) or so-called "normally open" (ie open in the basic position), 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 with the blow air valve la, the blow air source pl is not connected to the channel 11a and thus not to the injection molding tool 10. On the other hand, by opening the passage from connection 1 to 2 at the pre-air valve Ha, the pre-air source pH is indirectly connected to the air channel 11a and thus to the injection molding tool 10 via the open passage from connection 3 to 2 at 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 molding tool 10, which takes place between the molded parts and the corresponding cores of the injection molding tool 10 when the injection molding tool 10 is closed, the molded parts bulge (in particular the bases 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 detach from the injection molding tool 10 after a certain period of pre-air supply.

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 la into the vent line 12.

The air channel 11a is then subjected to the blowing air pressure from the blowing air source pl. To do this, the passage from connection 1 to connection 2 in the blowing air valve la must be opened, while the passage from connection 1 to connection 2 at the upstream pre-air valve Ha is closed (which is the case when connection 2 to connection 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 molding tool 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 molding tool 10 or to remove the molded parts from the injection molding tool 10 (typically assisted or even primarily accomplished by mechanical ejectors).

After the molded parts have been blown out by the blowing air supply for a desired period of time, the passage from connection 1 to 2 at the blowing air valve la is closed again by correspondingly controlling the blowing air valve la, so that the blowing air source pl is separated from the channel 11a. By closing the passage from connection 1 to 2 at the blowing air valve la, the passage from connection 2 to 3 at the blowing 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.

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).

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

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-load pressure on the check valve 17 can (intentionally) extend the duration of the release 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 11 a, 11 b 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 several connections E1, E2 on the injection mold 10, it can be advantageous to use several separate air ducts 11 a, 11 b in order to improve the process air supply. Each air duct 11 a, 11 b can be assigned its own valve pair la + lla, lb + llb, as shown in Fig. 2. A first valve pair consisting of the blow air valve la and the upstream pre-air valve Ha operates the first air duct 11 a. A second, parallel valve pair consisting of the blow air valve Ib and the upstream pre-air valve Hb operates the second air channel 11b. The two pre-air valves Ha, Hb are connected to the common pre-air source pH, while the two blow air valves la, Ib are connected to the common blow air source pl. Both air channels 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 la+lla and lb+llb are controlled in an identical manner, whereby the switching processes must be coordinated in detail depending on the size of the injection mold 10 in order to achieve the desired demolding sequence. For example, with 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 cost-effective and more dynamic (faster).

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

List of reference symbols

1 first valve connection for supply line

2 second valve connection for working line

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

10 Injection molding tool

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

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

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

12 Ventilation (line)

13 silencers

14 Electrical control of the valve

15 adjustable pressure control valve

16 compressed air storage

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

100 Device for providing process air

E1 , E2 Air inlet into the injection mold

Ea, Eb Air inlet into the injection mold

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

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

Ib first valve of valve pair b, 3/2-way valve (with electrical actuation) for blowing air

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

Expectations 1. Device (100) for an injection molding machine with an injection molding tool (10) for providing process air at a first and a second pressure that is different in comparison thereto, characterized in that the device (100) has a serial arrangement of two valves (la, Ha; Ib, Hb), the first valve (la; Ib) being connected on the one hand to a first pressure source (pl) with the first pressure and on the other hand to a channel (11a; 11b) which leads into the injection molding tool (10), and the second valve (Ha; Hb) being connected to a second pressure source (pH) with the second pressure and to a vent line (12), the first and second valves (la, 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 (la, Ha; Ib, Hb) are 3/2-way valves, each of which has 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 (la, Ib) is connected to the first pressure source (pl), the second connection (2) of the first valve (la; Ib) is connected to the channel (11a; 11b), and the third connection (3) of the first valve (la; 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 Exhaust 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 (la; Ib) and the second valve (Ha; Hb), wherein the further valve is connected to a further pressure source with a different further pressure compared to the first and second, wherein the first (la; Ib), second (Ha; Hb) and further valves 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 (la; Ib), 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 (la, Ha; Ib, Hb) in order to subject the channel (11a; 11b) to the first or second or optionally further pressure. 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 still 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 molding tool (10) and a device (100) according to one of claims 1 to 9, wherein the device (100) is connected to the injection molding tool (100) via one or more channels (11 a, 11 b) in order to be able to introduce process air into the injection molding tool (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 molding tool (10) or from a surface of the injection molding tool (10) and/or to eject molded parts from the injection molding tool, 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) 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. 13. 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 molding tool (10) in an injection molding 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 molding process, in particular during a cooling phase of the molded parts in the injection molding tool (10) of the injection molding 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 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 to arch the respective molded part, in particular 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 is conversely 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, pl) in the device (100) and the blowing air source is conversely either the first or second pressure source (pl, pH) in the device (100), and wherein the pre-air valve is either the second or first valve (Ha, la; Hb, Ib) in the device (100) and the blowing air valve is conversely 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. Method according to claim 13 or 14, with 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 demolding molded parts, in particular open hollow bodies, such as rotary bodies or cup-shaped molded parts, e.g. bottle closures, from an injection molding tool (10) during production by means of an injection molding machine.