Injection nozzle, mixing head, as well as device and method for controlling the discharge pressure

Abstract

Nozzle (10) for countercurrent injection of a liquid material for mixing with other components, comprising: - a nozzle housing (20) having at least one inlet opening (26) for supplying a liquid material and a nozzle outlet (22) for discharging the material, - wherein the nozzle housing (20) has a piston chamber (23) extending along a longitudinal axis (L) of the nozzle housing (20); - a nozzle piston (60) which is axially displaceable in the piston chamber (23) along the longitudinal axis (L) and separates a material chamber (24) and a pressure fluid chamber (25) from each other, - wherein a material surface (61) of the nozzle piston (60) can be subjected to a material pressure (PM) of the material and a pressure fluid surface (62) of the nozzle piston (60) can be subjected to a control pressure (PC) of a pressure fluid; - a nozzle needle (40) which is connected to the nozzle piston (60) and forms a variable nozzle opening (42) with the nozzle outlet (22); - a sealing device (70) that seals a circumferential gap (83) between the nozzle housing (20) and the nozzle piston (60), - wherein the control pressure (PC) in the pressure fluid chamber (25) is adjustable to control a discharge pressure (PA) of the material at the exit from the nozzle opening (42), wherein - the sealing device (70) comprises first and second sealing elements (71a, 71b), characterized by the fact that - the nozzle piston (60) forms a receptacle (68) for the sealing device (70), - the sealing device (70) has a sealing retaining ring (63) with circumferential recesses (67a, 67b) for receiving sealing elements (71a, 71b), - from the material surface (61) at least one connecting channel (66a) between the material chamber (24) and a circumferential recess (67a) and - at least one connecting channel (66b) is formed between the pressure fluid surface (62) and a circumferential recess (67b), - the first and second sealing elements (71a, 71b) are each designed as a sealing ring with a C-profile and a lateral circumferential groove (72a, 72b), - wherein the circumferential groove (72a) of the first sealing element (71a) is oriented towards the material surface (61) and the circumferential groove (72b) of the second sealing element (71b) is oriented towards the pressure fluid surface (62), - wherein the sealing element (71a, 71b) expands in a radial direction when the circumferential groove (72a, 72b) is filled with a pressurized liquid, for example the material or the pressurizing fluid.

Description

[0001] The invention relates to a nozzle, in particular an injection nozzle for countercurrent injection of a liquid material for mixing with other components, a mixing head with such a nozzle, as well as a device and a method for controlling the discharge pressure of the material when exiting a nozzle.

[0002] To manufacture components from multiple materials, several liquid materials are often mixed together to form a reaction mixture. For example, the so-called countercurrent injection molding (RIM) process is well-known for producing plastic molded parts, particularly for manufacturing foamed components from polyurethane foam. In this process, two material components are typically injected against each other under high pressure through opposing nozzles into a mixing chamber. Utilizing the kinetic energy or momentum of the jets from the nozzles, a reaction mixture is generated. To produce a component, the resulting mixture is then poured into a mold to cure.Counterflow injection molding is used for the production of polyurethane molded parts, for example, for the automotive industry, for insulating layers in refrigerators, or for insulating panels in refrigerated vehicles. Suitable injection nozzles, mixing heads, and systems for counterflow injection are generally known in the art. Known nozzles in which the back pressure on the nozzle piston is provided by an elastic spring typically require additional damping, as they otherwise tend to overshoot (oscillate). This damping, in turn, leads to detrimental dynamic behavior of the nozzle.

[0003] From WO 97 / 32 705 A1 a mixing head for mixing two components by countercurrent injection to produce a reactive mixture, e.g. for processing polyurethane, is known.

[0004] DE 100 20 157 A1 describes an injection nozzle with a rear hydraulically actuated nozzle piston, which is sealed against the material chamber by means of a metallic bellows.

[0005] DE 10 2007 037 780 A1 describes a constant pressure nozzle with a bellows that can be hydraulically actuated with a control pressure. Alternatively, a compression spring is provided as a flexible control element, wherein the space in which the flexible control element moves is hydraulically sealed from a material chamber. The control pressure is to be reduced relative to the material pressure.

[0006] WO 2014 / 009172A1 describes a component feed nozzle with a pressure chamber that can be pressurized hydraulically or pneumatically. The pressure chamber is sealed off from the component chamber by a diaphragm seal to allow for more precise responses to changes in the quantity of components.

[0007] Injection devices and mixing heads are known from DE 32 00 802 A1 and DE 30 18 381 A1.

[0008] To ensure consistently high component quality, both within a single component and over a longer production process of series components, the goal is to achieve the most homogeneous possible mixing of the injected material components.

[0009] Production systems designed for flexible use with various components of different sizes and hardnesses must ensure thorough mixing of the material components at varying mass flow rates and discharge pressures. Depending on the manufacturing requirements, the discharge mass flow rate and / or discharge pressure of the materials through the nozzles can change from shot to shot, for example, to vary the foam density of a component or because different shot weights are required depending on the component size.

[0010] Even during a single nozzle stroke, consistently good mixing is essential. A common problem is that the mass flows of material components conveyed from a metering system to a nozzle are subject to local variations in material parameters during a single stroke. For example, a local temperature change, such as a colder material bubble being conveyed along with the dispensed material, can lead to a local variation in...

[0011] Viscosity changes can occur. Furthermore, the mass flow rate delivered by a metering pump can vary due to changes in the delivery rate. These variations can impair the mixing of the material components.

[0012] The nozzles known from the prior art only partially meet the aforementioned requirements for the most homogeneous possible mixing of the different materials. Furthermore, problems with sealing the nozzle piston are known to occur with prior art nozzles, especially at high discharge pressures.

[0013] Based on this prior art, the present invention aims to provide a nozzle, a mixing head, a device, and a method for mixing liquid material components to achieve improved component quality. In particular, consistently good mixing of the materials should be ensured for components or component properties that vary from shot to shot, and especially during a single shot. Therefore, the invention also aims to create a nozzle that is as flexible as possible in its application.

[0014] This problem is solved by a nozzle according to claim 1, a mixing head according to claim 8, claim 11, as well as by a device and a method for controlling the discharge pressure of a material when exiting a nozzle according to claim 9 or 10.

[0015] In particular, the problem is solved by a nozzle, especially an injection nozzle, preferably for countercurrent injection of a liquid material for mixing with other components, comprising: - a nozzle housing that has at least one inlet opening for supplying a liquid material and one nozzle outlet for discharging the material, wherein the nozzle housing has a piston chamber which extends along a longitudinal axis of the nozzle housing; - a nozzle piston which is axially displaceable in the piston chamber along the longitudinal axis and separates a material chamber and a pressure fluid chamber from each other, wherein a material surface of the nozzle piston can be subjected to a material pressure of the material and a pressure fluid surface of the nozzle piston can be subjected to a control pressure of a pressure fluid; - a nozzle needle that is connected to the nozzle piston and forms a variable nozzle opening with the nozzle outlet; - a sealing device that seals a circumferential gap between the nozzle housing and the nozzle piston, wherein the control pressure in the pressure fluid chamber is adjustable, preferably hydraulically, in order to control the discharge pressure of the material when exiting the nozzle opening.

[0016] Based on the understanding that fluctuations in the material's discharge pressure at the nozzle exit can impair the mixing of the materials being dispensed, the invention is based on the idea of ​​regulating the material's discharge pressure at the nozzle exit in such a way that it is kept constant during a shot and can be adjusted to a desired (constant) discharge pressure from shot to shot. Preferably, the discharge pressure is kept as constant as possible over the entire duration of a shot. This ensures homogeneous mixing of the different materials within a component and for different components.

[0017] The mixing of materials from opposing nozzles depends on the momentum of the colliding material jets, which in turn depends on their mass flow rates and discharge velocities. The discharge velocity, in turn, depends on the discharge pressure. By adjusting the discharge pressure, the mixing point resulting from the momentum of the material jets can be kept approximately constant, preferably exactly midway between the nozzles of the colliding material jets. This ensures a consistently high mixing quality of the injected material components.

[0018] Liquid materials within the meaning of the invention can be, in particular, liquid plastics or resins, which are preferably mixed together to produce a reaction mixture. The nozzle according to the invention is particularly suitable for the production of polyurethane (PU or PUR).

[0019] For example, a liquid material is a diol or a polyol, or a diisocyanate or a polyisocyanate. A pressure fluid is, in particular, a hydraulic fluid, such as water or oil.

[0020] The nozzle housing can be multi-part, in particular rotationally symmetrical about the longitudinal axis. The piston chamber is preferably located inside the nozzle housing, preferably has a circular cylindrical shape, and is preferably bounded radially by one or more circumferential inner surfaces of the nozzle housing. The nozzle piston can be made in one or more parts. The nozzle needle can be formed integrally with the nozzle piston or attached to it.

[0021] The material surface and the pressure fluid surface can be the same size or different sizes, especially in a projection in the direction of the longitudinal axis, and in particular essentially the same size.

[0022] The nozzle piston is movable back and forth, preferably continuously, between a front end position in which the nozzle opening is closed and a rear end position in which the nozzle opening is maximally open. The front and rear end positions define, in particular, the maximum stroke of the nozzle piston. In the front end position, the nozzle needle rests against a sealing seat, preferably metallic. In the rear end position, the nozzle piston rests, preferably with a rear stop surface, against a rear wall of the pressure fluid chamber. The size of the nozzle opening is variably adjustable, in particular by moving the nozzle piston along its longitudinal axis. Specifically, the nozzle outlet interacts with the nozzle pin in such a way that, when the nozzle is open, an annular gap is formed within the nozzle opening.

[0023] The circumferential gap extends particularly in the direction of the longitudinal axis between the nozzle housing and the nozzle piston, and preferably shifts accordingly when the nozzle piston is displaced relative to the nozzle housing. The circumferential gap is particularly designed in the form of a hollow cylinder, or several stepped hollow cylinder segments of different diameters, preferably with annular cross-section.

[0024] The sealing device seals the material chamber, in particular against the pressure fluid chamber. Preferably, the sealing device is designed such that no pressure fluid can pass from the pressure fluid chamber into the material chamber, or vice versa, through the circumferential gap. The sealing device can be mounted or housed in the nozzle housing or in the nozzle piston, or alternatively, it can be divided into two parts, partially in the nozzle housing and partially in the nozzle piston. In particular, the sealing device acts as a sliding seal. When the nozzle piston is displaced, the sealing device slides, in particular, along an inner circumferential surface of the nozzle housing or along an outer circumferential surface of the nozzle piston.

[0025] The control pressure in the pressure fluid chamber is adjustable or adaptable, particularly hydraulically, preferably electrohydraulically, for example by an electrically or electronically controlled valve, preferably a proportional valve, which causes a controlled inflow and outflow of pressure fluid into the pressure fluid chamber. In particular, the axial position of the nozzle piston is adjusted according to the pressure difference between the material pressure and the control pressure. Specifically, by adjusting a control pressure that differs from the material pressure, the nozzle piston can be moved such that the discharge pressure can be regulated via the correspondingly adjusted nozzle opening. It can be assumed, in particular, that a material pressure measured, for example, in the material chamber or a feed line, corresponds at least to a good approximation to the discharge pressure of the material at the exit of the nozzle opening. The pressure fluid chamber is preferably ventable.

[0026] A nozzle according to the invention has the advantage that the discharge pressure can be regulated to an at least approximately constant value. The nozzle is particularly suitable for regulating the discharge pressure so that it corresponds to a desired or predetermined target discharge pressure. The discharge pressure can be kept constant during a single shot and can optionally be varied from shot to shot. It is also conceivable to specify a particular pressure profile for the discharge pressure during a single shot. Fluctuations in material parameters or mass flow can be compensated for during a shot through the nozzle. The nozzle according to the invention can be regulated quickly, particularly with a high control frequency and low delay, which allows for more precise adjustment and readjustment of the discharge pressure.A constant discharge pressure ensures more homogeneous mixing of the materials, thereby improving component quality. Furthermore, the nozzle can be opened and closed quickly, making it particularly suitable for short or rapidly successive shots. A control system based on setting a control pressure of the pressure fluid, preferably hydraulic, offers the advantage of enabling a large maximum stroke of the nozzle piston. In particular, only small volumes of pressure fluid need to be moved to achieve a specific stroke of the nozzle piston. This allows for the discharge of very different mass flow rates of a material using the same nozzle. Specifically, the mass flow rate can be varied over a wide range from shot to shot. A nozzle according to the invention is highly flexible and can be used for various components, component properties, and / or materials to be discharged.

[0027] In an advantageous embodiment of the nozzle according to the invention, the nozzle piston forms a receptacle for the sealing device, wherein the sealing device in particular comprises a sealing retaining ring having circumferential recesses for receiving sealing elements. The receptacle of the nozzle piston for the sealing device is in particular designed as a shoulder of the nozzle piston onto which, in particular, a sealing retaining ring can be slid, preferably from the rear. The circumferential recesses of the sealing retaining ring are preferably designed as recesses along the outer circumferential edges of the sealing retaining ring. Alternatively or additionally, circumferential recesses for receiving sealing elements can be provided in an outer circumferential surface of the sealing retaining ring. In particular, the nozzle piston has a circumferential radial projection.Preferably, a front face of the radial projection forms at least part of the material surface. The rear face of the radial projection preferably forms a stop surface for the axial support of the sealing device or the sealing retaining ring. A rear axial stop for the sealing device or the sealing retaining ring is formed, for example, by a piston cover. A piston cover can be clamped to the nozzle piston, for example, by a screw, wherein the preferably ground surface of the screw head forms, in particular, a rear stop surface of the nozzle piston, e.g., for a stop against a rear wall of the pressure fluid chamber. A sealing device accommodated in the nozzle piston has the advantage that the piston chamber can be manufactured easily, for example, by drilling a hole into the nozzle housing from the rear, while the nozzle piston can be pre-assembled with the sealing device.

[0028] In an advantageous embodiment of the nozzle according to the invention, the sealing device comprises first and second sealing elements, which are preferably designed as sealing rings, ideally with a circumferential groove. In particular, the sealing elements are arranged axially spaced apart from one another, preferably with exactly two sealing elements being provided, e.g., a front and a rear sealing element. The sealing elements extend, in particular, along an outer circumferential surface of the sealing piston or the sealing retaining ring. Preferably, the sealing elements are designed as sliding seals that can slide, in particular, along an inner circumferential surface of the nozzle housing in the axial direction. The sealing elements can, in particular, be pre-assembled on the sealing retaining ring, preferably by being placed or slid onto the sealing retaining ring from the front or rear.Sealing elements preferably have a lateral circumferential groove, with the circumferential groove of the first (front) sealing element preferably oriented towards the material surface and the circumferential groove of the second (rear) sealing element oriented towards the pressure fluid surface. The sealing elements or sealing rings can have a variety of different profiles, e.g., a C-profile or other hollow profiles, including asymmetrical profiles. A circumferential groove is particularly well-designed in the sealing element, e.g., U-shaped or pear-shaped, such that the sealing element expands radially when the circumferential groove is filled with a pressurized liquid, for example, the material or the pressure fluid. In this way, an increased sealing effect can be achieved by radially pressing the sealing element against an inner circumferential surface (sliding surface) of the nozzle housing.Two or more sealing elements have the advantage that the circumferential gap can be sealed more reliably.

[0029] In an advantageous embodiment of the nozzle according to the invention, the first and / or second sealing elements comprise PTFE, preferably a PTFE compound. Polytetrafluoroethylene (PTFE) has good sliding properties as well as good chemical and thermal resistance. A PTFE compound or PTFE-based compound (plastic) can contain various added fillers to achieve specific material properties. Preferably, the material composition of the sealing elements is matched to the surface structure, in particular the cross-sectional pattern, of the sliding surface or a circumferential inner surface of the nozzle housing. A sealing lubricating film can form between the sealing elements and the sliding surface of the nozzle housing. In an alternative embodiment, the first and / or second sealing elements can have a PTFE coating, at least along their outer circumference.Sealing elements made of or containing PTFE have the advantage that the circumferential gap can be reliably sealed with minimal friction. For a nozzle according to the invention, this allows for high stroke speeds of the nozzle piston and a high control frequency. The dynamic behavior of the nozzle is improved insofar as, in particular, no stick-slip effect occurs during displacement of the nozzle piston, and there are significantly reduced delays in the nozzle's start-up behavior. This enables the nozzle piston to execute rapid, and especially small, strokes. The discharge pressure can therefore be adjusted more precisely.

[0030] In an advantageous embodiment of the nozzle according to the invention, at least one connecting channel is formed from the material surface between the material chamber and a circumferential recess, and / or at least one connecting channel is formed from the pressure fluid surface between the pressure fluid chamber and a circumferential recess. A connecting channel is, in particular, designed as a through-opening in the nozzle piston, preferably in a radial projection of the nozzle piston, e.g., as a bore. For example, 4 to 16, preferably 6 to 12, and particularly preferably 8, bores are provided, distributed evenly around the circumference. The connecting channels, in particular, establish a fluid connection between a circumferential recess and the material chamber or the pressure fluid chamber, so that the pressurized material or the pressure fluid can be transferred to the material chamber or the pressure fluid chamber.The pressurized fluid, by filling the sealing element, can exert pressure against the sliding surface of the nozzle housing, and optionally also against an outer surface of the sealing retaining ring. In an alternative, but not preferred, embodiment, axial connecting grooves, preferably evenly distributed around the circumference, are formed in an outer circumferential surface of the nozzle piston. Connecting channels have the advantage that the material or the pressurized fluid does not first have to penetrate the circumferential gap. The dynamic behavior of the nozzle is improved in this way. In particular, nozzle start-up times can be shortened and the control frequency increased.

[0031] In an advantageous embodiment of the nozzle according to the invention, a monitoring opening is provided in the nozzle housing, to which a pressure sensor can preferably be connected in order to monitor the pressure in a piston gap between the first and second sealing elements. A piston gap is defined, in particular, between a first (front) and a second (rear) sealing element and can be understood as a (time-shifting) section of the circumferential gap. A monitoring opening is preferably designed as a (radial) bore in the nozzle housing and preferably opens into the piston gap. Several monitoring openings can be provided, preferably distributed (uniformly) around the circumference. Through a monitoring opening, an unforeseen ingress of liquid material or pressurized fluid into the piston gap can be monitored.A pressure sensor can detect pressure changes in the piston space, which may indicate a defect in one of the sealing elements. The piston space can be pressurized to a reference pressure level, which can be monitored through the monitoring port. This reference pressure level can be selected independently of the material pressure and / or control pressure. Monitoring the piston space allows for the timely detection of pressurized fluid ingress into the material chamber. In an advantageous embodiment of the nozzle according to the invention, a collecting groove is formed in the nozzle housing. This groove opens into the piston space between the first and second sealing elements and is preferably connected to the monitoring port. In this way, the piston space can be monitored around its entire circumference, particularly by a single pressure sensor.

[0032] In an advantageous embodiment of the nozzle according to the invention, the maximum stroke speed of the nozzle piston during nozzle operation is between 1 m / s and 15 m / s, preferably between 5 m / s and 10 m / s, more preferably between 6 m / s and 9 m / s, and more preferably approximately 8 m / s. A high stroke speed allows for high control frequencies for the nozzle. The discharge pressure can be adjusted more precisely. Furthermore, the nozzle can be opened and closed quickly. This reduces the start-up phase required to set a predetermined discharge pressure.

[0033] In an advantageous embodiment of the nozzle according to the invention, the maximum stroke of the nozzle piston is more than 1.0 mm, preferably more than 1.5 mm, more preferably more than 2.0 mm, more preferably more than 2.5 mm, and more preferably more than 3.0 mm. In a forward end position of the nozzle piston, in which the nozzle needle rests against a sealing seat, the maximum stroke of the nozzle piston corresponds to the free distance between a rear stop surface of the nozzle piston and a stop surface, e.g., a rear wall, of the pressure fluid chamber. In a preferred embodiment of the nozzle according to the invention, the maximum stroke is approximately 1.7 mm. A large maximum stroke can be achieved, in particular, by hydraulically controlling the nozzle, since only small volumes of fluid need to be moved. The nozzle is thus flexibly usable for different mass flow rates.

[0034] In an advantageous embodiment of the nozzle according to the invention, the nozzle needle has a nozzle pin that forms an annular gap with the nozzle outlet, wherein the nozzle pin preferably has a diameter between 0.5 mm and 10 mm, more preferably between 1 mm and 5 mm, for example 1.0 mm, 2.0 mm, 3.5 mm or 4.0 mm. The nozzle pin preferably has a length between 0.5 mm and 2 mm, more preferably between 0.7 mm and 1.5 mm, for example approximately 1.0 mm. Preferably, in the closed state of the nozzle, the nozzle pin forms an annular gap with the nozzle outlet with a constant cross-section, e.g. over a length of approximately 0.5 mm of the nozzle pin. In this way, the nozzle opening initially remains unchanged during the start-up phase after opening the nozzle, in order to improve the unsteady start-up behavior of the nozzle. By selecting the diameter of the nozzle pin, orThe nozzle outlet of the nozzle according to the invention can be designed for the discharge of a specific range of mass flows. Furthermore, a nozzle pin can ensure that the flow remains laminar in the area of ​​the nozzle opening. This allows for a consistently uniform annular jet of material to be achieved, preferably also independent of the degree of opening of the nozzle.

[0035] The aforementioned problem is further solved in particular by a mixing head, especially for counter-current injection mixing of liquid materials, comprising a mixing chamber and at least two nozzles directed towards each other, in particular injection nozzles, wherein in particular at least two groups of at least two nozzles directed towards each other, in particular two pairs of opposing nozzles, are provided, and preferably a post-mixing chamber is arranged between the groups, characterized in that at least one of the nozzles is designed according to the invention.

[0036] A mixing head according to the invention is preferably designed as a deflection mixing head, wherein the material discharged from the nozzles is deflected, for example, by 90° in a post-mixing chamber. The mixing head can comprise different nozzles, in particular at least two different nozzles according to the invention, which are designed, for example, for different mass flow ranges. Different mass flows of different materials, especially with different densities, can be discharged for mixing in one mixing head. In particular, the discharge pressures of the nozzles of the mixing head can each be adjusted to a different value. During operation of the mixing head, individual nozzles of the mixing head can be closed while other nozzles of the mixing head are in operation. Preferably, all nozzles of the mixing head can be opened and / or closed simultaneously.A mixing head with lockable nozzles eliminates the need for a separate sealing unit, in particular shut-off valves for material pressure.

[0037] A mixing head according to the invention has the advantage that the discharge pressure of each nozzle can be adjusted separately and kept as constant as possible. Such a mixing head is easily configurable for different mass flow ratios. For example, the mass flow ratio between two nozzles or between two successive shots from a nozzle can be in the range of 1:1 to 1:5 or the corresponding reciprocals. For example, a dischargeable mass flow rate can be between 500 g / s and 2500 g / s. The mixing point can be kept constant both during a single shot and from shot to shot, preferably in the middle between the nozzles. This improves the component quality. A mixing head according to the invention is versatile in its application.

[0038] The aforementioned problem is further solved in particular by a device for regulating the discharge pressure of a material when exiting a nozzle, in particular an injection nozzle, preferably for countercurrent injection of a liquid material for mixing with other components, comprising: - at least one nozzle, in particular a nozzle according to the invention, preferably a mixing head according to the invention; - a metering pump connected to the nozzle via a supply line to supply the nozzle with a liquid material; - a pressurized fluid reservoir connected to the nozzle via a pressurized fluid line to supply the nozzle with pressurized fluid; - a valve, in particular a proportional valve, for setting a control pressure of the pressure fluid in a pressure fluid chamber of the nozzle; - a pressure sensor to detect the material pressure of the material; - a control unit designed to actuate the valve, preferably hydraulically, based on a pressure deviation of the detected material pressure from a predetermined target discharge pressure, in order to adjust the control pressure.

[0039] A device according to the invention particularly forms a control loop, wherein the discharge pressure of the material at the exit from the nozzle opening is preferably the controlled variable, and a predetermined target discharge pressure is preferably the reference variable. The control pressure in the pressure fluid chamber can be understood as the manipulated variable. It can be assumed that the detected material pressure corresponds at least to a good approximation to the discharge pressure of the material at the exit from the nozzle opening. In this way, the control pressure in the pressure fluid chamber can be adjusted based on a pressure deviation between the detected material pressure and the predetermined target discharge pressure, preferably according to a control implemented by the control unit, such that the discharge pressure of the material is regulated to the predetermined target discharge pressure.

[0040] The control unit comprises, in particular, a processing unit such as a microprocessor or a CPU, and is specifically designed to calculate a pressure deviation (pressure difference) between a predetermined target discharge pressure, stored in a memory unit, and a measured material pressure. The control unit is specifically designed to generate a control command for actuating the valve based on the calculated pressure deviation. The pressure sensor for detecting the material pressure can be arranged, for example, in the material chamber, at an inlet opening, or in a feed line of the nozzle. Optionally, a pressure sensor for detecting the control pressure can be provided, for example, in the pressure fluid line. Preferably, the device according to the invention includes a pressure sensor for monitoring the pressure in the piston space, wherein the pressure sensor is, in particular, connected to a monitoring opening of the nozzle housing.The material pressure is controllable, in particular via the metering pump. When the nozzle is closed, material fed to the nozzle can circulate through the feed and return lines, preferably via a circumferential channel formed in the material chamber. The return lines are preferably closable, especially when the nozzle is open, i.e., during a shot.

[0041] The inlet pressure, preferably supplied to the valve from the pressure fluid reservoir, is preferably between 200 bar and 300 bar, more preferably between 220 bar and 280 bar, more preferably between 240 bar and 260 bar, and particularly preferably approximately 250 bar. A proportional valve is preferably provided for adjusting the control pressure in the pressure fluid chamber, which adjusts the control pressure in the pressure fluid chamber proportionally to the pressure deviation. The proportional valve is particularly actuated by a proportional solenoid. The control pressure in the pressure fluid chamber is preferably between 50 bar and 200 bar, more preferably between 80 bar and 170 bar, more preferably between 100 bar and 150 bar, for example approximately 125 bar. The material pressure during material discharge is preferably approximately in the range of the control pressure.

[0042] A device according to the invention is based in particular on the same functionality and has the same advantages as previously described for a nozzle and a mixing head according to the invention. In particular, such a device is flexible in its application and can improve component quality.

[0043] The aforementioned problem is further solved in particular by a method for controlling the discharge pressure of a material upon exiting a nozzle, in particular an injection nozzle, preferably for countercurrent injection mixing, in particular from a nozzle according to the invention, wherein a slidably mounted nozzle piston of the nozzle separates a material chamber and a pressure fluid chamber from one another and a material surface of the nozzle piston can be subjected to a material pressure of the material and a pressure fluid surface to a control pressure of a pressure fluid, wherein the method comprises the following steps: - Storing a target discharge pressure, with which a material is to be discharged from the nozzle, in a control unit; - Conveying a material into the material chamber of the nozzle using a metering pump; - Detecting material pressure using a pressure sensor; - Transferring the recorded material pressure to the control unit; - Determining the pressure deviation of the material pressure from the predetermined target discharge pressure by the control unit; - Setting a control pressure in the pressure fluid chamber, preferably hydraulically, in particular by actuating a valve, in particular a proportional valve, based on the pressure deviation, preferably at least once during a shot of the nozzle.

[0044] In particular, the pressure deviation is calculated by the control unit, which preferably generates a control command to actuate the valve. The control command is transmitted, in particular, to a valve controller. Preferably, the proportional valve is actuated based on the control command, especially by stepless adjustment. The control pressure can be set by adding or removing a volume of pressure fluid into or out of the pressure fluid chamber. In particular, if the material pressure is lower than the target discharge pressure, the control pressure is increased, and if the material pressure is higher than the target discharge pressure, the control pressure is reduced. The target discharge pressure can be changed from one shot to the next from the nozzle, and in particular, it can be reset.

[0045] The method according to the invention comprises, in particular, a step of monitoring the functionality of a sealing device, especially by monitoring a piston gap between two sealing elements. In particular, the pressure level, for example a reference pressure level, in the piston gap is monitored by a pressure sensor. In particular, it can be checked by means of a monitoring opening whether liquid material and / or pressurized fluid has entered the piston gap.

[0046] The method has similar advantages to those already described in connection with the nozzle, the mixing head and the device according to the invention and can implement some or all of the process engineering features described in connection with the nozzle, the mixing head or the device.

[0047] In an advantageous embodiment of the method according to the invention, the control pressure is adjusted at least 100 times per second, more preferably at least 250 times per second, more preferably at least 500 times per second, more preferably at least 750 times per second, and more preferably approximately 1000 times per second. In particular, the control pressure is adjusted during a nozzle shot at corresponding control frequencies, preferably by actuating or adjusting the proportional valve at such a frequency.

[0048] An advantageous further development of the method according to the invention comprises the following steps: - Closing the nozzle by setting a control pressure that is higher than the material pressure, and / or - Opening the nozzle by setting a control pressure that is lower than the material pressure, and / or - Adjusting a nozzle opening of the nozzle for the discharge, preferably injection, of the material by setting a control pressure that is at least substantially the same as the material pressure.

[0049] In particular, a nozzle according to the invention is suitable for selectively performing all of these process steps. Preferably, a nozzle according to the invention can be operated in three different operating modes, in particular in a closing mode, an opening mode, and a discharge mode. In a discharge mode (injection mode), the nozzle discharges or injects material at a controlled discharge pressure. To close the nozzle, a control pressure is set in the pressure fluid chamber that exceeds the material pressure by up to 50 bar, preferably up to 30 bar, more preferably up to 20 bar, and more preferably up to 10 bar, for example, by approximately 5 bar. Sufficient overpressure ensures that the nozzle remains securely closed even with fluctuations in the material pressure. To open the nozzle, the control pressure is reduced to a lower level than the material pressure, preferably until the nozzle reaches a desired degree of opening.To fully open the nozzle, particularly to its rear stop, a permanently lower control pressure can be set. Specifically, the nozzle piston moves according to the pressure difference between the material pressure and the control pressure until an equilibrium is reached between the material chamber and the pressure fluid chamber, specifically until a resulting force equilibrium is established on the nozzle piston across the material surface (and the projected surface of the nozzle needle on which the material pressure acts) and the pressure fluid surface. In particular, when the force acting axially on the nozzle piston from the control pressure is equal to the force acting axially on the nozzle piston from the material pressure, the nozzle piston maintains its axial position and the nozzle opening does not change.In a regulated state, the discharge pressure is maintained at a constant value, which preferably corresponds to the target discharge pressure, wherein the discharge pressure and the material pressure are equal and preferably form a force equilibrium with the control pressure, wherein the control pressure is preferably at least substantially equal to the material pressure.

[0050] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. These show: Fig. 1A a schematic representation of an embodiment of a nozzle according to the invention in a side view; Fig. 1B a schematic representation of the nozzle according to the invention Fig. 1A in a rear view; Fig. 1C a schematic representation of the nozzle according to the invention Fig. 1A in a sectional view along line AA; Fig. 1D a detailed view of the dashed area C in Fig. 1C; Fig. 1E a detailed view of the front area B of the nozzle in Fig. 1C; Fig. 2 a detailed view of a further embodiment of a nozzle according to the invention in a sectional view, which Fig. 1E corresponds to; Fig. 3 a schematic representation of an embodiment of the device according to the invention for regulating the discharge pressure.

[0051] In the following description of the invention, the same reference numerals are used for identical and identically acting elements.

[0052] The Fig. Figures 1A to 1E show an embodiment of a nozzle 10 according to the invention, which is particularly suitable for injecting a liquid material for mixing with other components in a countercurrent injection process. The nozzle 10 is rotationally symmetrical about the longitudinal axis L and comprises a nozzle housing 20 and a nozzle block 50, which can be connected, for example, to a mixing head according to the invention (not shown) via fastening means 51, here designed as screws. The nozzle housing 20 is screwed into a recess 52 of the nozzle block 50. As shown in Fig. As shown in Figure 1B, the nozzle block 50 has a pressure fluid port 54 and a vent port 55 on its rear side, which are connected to a pressure fluid inlet 28 and a vent opening 29 of the pressure fluid chamber 25, respectively. The venting of the pressure fluid chamber 25 can be provided, for example, by a pneumatic ball valve or a vent needle.

[0053] The nozzle housing 20 has inlet openings 26 and return openings 27, which are designed as eight bores evenly distributed around the circumference in a star shape and are intended for connecting a supply line 6a and a return line 6b, respectively. The function of a bore as an inlet opening 26 or return opening 27 is determined by the mounting orientation of the nozzle 10. Paired circumferential seals 30 and 36, designed as O-rings, serve for sealing. The nozzle housing 20 has a nozzle outlet 22 on its front for discharging a liquid material.

[0054] The nozzle housing 20 has a piston chamber 23 with a circular cylindrical base shape, in which a nozzle piston 60 is axially displaceable along the longitudinal axis L in a guide section 35 of the nozzle housing 20. The nozzle piston 60 is formed in one piece with a nozzle needle 40, which forms a circular cylindrical nozzle pin 41 at its front. A nozzle opening 42 in the form of an annular gap is formed between the nozzle pin 41 and the nozzle outlet 22. A piston cover 64 is screwed onto the nozzle piston 60 from the rear by a screw 65. The nozzle piston 60 is movable back and forth between a front end position, in which the nozzle needle 40 rests against a metallic sealing seat 34, and a rear end position, in which the ground surface of the screw 65 rests against the rear wall of the pressure fluid chamber 25 as a rear stop. These two end positions define the maximum stroke of the nozzle piston 60.The rear wall of the pressure fluid chamber 25 is formed here by the nozzle block 50.

[0055] The nozzle piston 60 separates the piston chamber 23 into a material chamber 24 and a pressure fluid chamber 25. The pressure fluid chamber 25 is sealed to the outside by a seal 53, designed as an O-ring. A narrow circumferential gap 83 forms between the nozzle housing 20, in particular its inner circumferential surface 84, and the nozzle piston 60, which is sealed by the sealing device 70. The material chamber 24 is connected to the inlet openings 26 and return openings 27 via material passages 32 and material channels 31, each designed as bores. A circumferential channel 33 is formed around the nozzle needle 40, through which the material can circulate when the nozzle 10 is closed.In an operating state of the nozzle 10, the material chamber 24 is filled with a liquid material to be discharged, which exerts the material pressure PM on the material surface 61 at the front of the nozzle piston 60, while the pressure fluid chamber 25 is filled with a pressure fluid that exerts the control pressure PC on the pressure fluid surface 62 at the rear of the nozzle piston 60. Here, the material surface 61 is smaller than the pressure fluid surface 62 in a projection along the longitudinal axis L, with the material pressure PM also acting on the surface of the nozzle needle 40.

[0056] The nozzle piston 60 forms a receptacle 68, designed as a shaft shoulder, to receive a seal retaining ring 63 of the sealing device 70. A radial projection 69 of the nozzle piston forms a front stop surface for the sealing device 70, while the piston cover 64 forms a rear stop surface. The seals 73, designed as O-rings, are inserted into circumferential grooves of the nozzle piston 60. The seal retaining ring 63 has circumferential recesses 67a, 67b on both sides along the outer circumferential edges with a rectangular cross-section, into which the first and second sealing elements 71a, 71b are inserted. The sealing elements 71a, 71b are designed as grooved sealing rings. They have a C-shaped cross-section and have lateral circumferential grooves 72a, 72b, which are oriented towards connecting channels 66a and 66b, respectively. Liquid material can pass through the connecting channels 66a and 66b.Inject pressurized fluid into the circumferential grooves 72a, 72b and expand the sealing elements radially. This causes the sealing elements 71a, 71b to press against the inner circumferential surface 84 from the inside, forming a sliding surface for the sealing elements 71a, 71b. This reliably seals the circumferential gap 83. The sealing elements 71a, 71b are made of a PTFE compound with good sliding properties.

[0057] A piston gap 80 forms between the first sealing element 71a and the second sealing element 71b, which can also be considered a section of the circumferential gap 83. A circumferential collecting groove 82 is formed in the inner circumferential surface 84, into which several monitoring openings 81, evenly distributed around the circumference, open. These monitoring openings are designed as through-holes in the nozzle housing 20. The proper functioning of the sealing device 70 can be monitored through these monitoring openings 81. For example, a pressure sensor 3 connected to a monitoring opening 81 (see Figure 1) can be used to detect the pressure in the nozzle housing. Fig. 3) The pressure level in the piston space 80 can be monitored. In particular, this allows monitoring of whether liquid material or pressurized fluid has entered the piston space 80, which would indicate a defect in the sealing device 70.

[0058] Fig. Figure 2 shows a further embodiment of a nozzle 10 according to the invention, which, compared to the nozzle 10 in Fig. 1E has a nozzle pin 41 and a nozzle outlet 22 with a larger diameter, for example 3.5 mm. Otherwise, the nozzle 10 is constructed and functions identically to the nozzle 10 according to the Fig. 1A to 1E.

[0059] Fig.Figure 3 shows an embodiment of a device 100 according to the invention for controlling the discharge pressure (PA) of a material as it exits a nozzle 10 according to the invention. Liquid material is supplied from a component container 7 to a metering pump 4 via a material line. The metering pump supplies the material at a material pressure PM to the material chamber 24 via a supply line 6a. A pressure sensor 2 is provided in the supply line 6a for detecting the material pressure PM. The material can circulate back to the component container 7 via a return line 6b, for example, when the nozzle 10 is closed. A pressure fluid reservoir 9 provides a pressure fluid, in particular a hydraulic fluid, at a pressure of, for example, up to 250 bar at a valve 5. The valve 5 is preferably designed as a proportional valve and sets the control pressure PC of the pressure fluid in the pressure fluid chamber 25 via a pressure fluid line 8.The pressure in the piston space 80 between two sealing elements of the sealing device 70 can be monitored by the pressure sensor 3 via a collecting groove 82 and a monitoring opening 81. The pressure sensors 2 and 3, as well as the valve 5, are connected to the control unit 1 via signal transmission. The control unit 1 calculates a pressure deviation between a predetermined target discharge pressure and the material pressure PM measured by the pressure sensor 2. Based on this pressure deviation (pressure difference), the valve 5, preferably a proportional valve, is actuated and adjusted according to the pressure deviation. Accordingly, the valve 5 sets the control pressure PC in the pressure fluid chamber 25 proportionally to the pressure supplied from the pressure fluid reservoir 9, in particular hydraulic pressure. The nozzle piston 60 moves axially according to the resulting pressure difference between the control pressure PC and the material pressure PM.The sealing device 70 slides along the inner circumferential surface 84 while reliably sealing the circumferential gap 83. The nozzle opening 42 changes as the nozzle piston 60 moves. The discharge pressure PA of the material at the exit of the nozzle opening 42 can thus be controlled, preferably to a constant value.

[0060] A nozzle 10 according to the invention can be operated in three different operating modes, namely a closing mode, an opening mode, and a discharge mode. To close the nozzle, a control pressure PC is set by actuating the valve 5, which is higher than the material pressure PM. As a result, the nozzle piston 60 moves to a first end position, where it reaches a stop against a nozzle seat 34 and closes the nozzle opening 42. To open the nozzle 10, a control pressure PC is set by actuating the valve 5, which is lower than the material pressure PM. Consequently, the nozzle needle 40 initially opens a constant annular gap of the nozzle opening 42 and then progressively enlarges the nozzle opening 42, up to a maximum of 100 degrees, until the nozzle piston 60 reaches a second end position against a rear stop. In this state, the nozzle 10 can discharge a maximum mass flow rate.In discharge mode, the nozzle opening 42 is continuously adjusted (i.e., readjusted) by a control pressure PC at a high control frequency so that the discharge pressure PA is regulated to a value that is as constant as possible. This results in a force equilibrium on the nozzle piston 60, whereby the control pressure PC is at least essentially equal to the material pressure PM.

[0061] A nozzle 10 according to the invention, a mixing head with such a nozzle 10, as well as a device 100 according to the invention and a method for controlling the discharge pressure PA have the advantage that, by maintaining a discharge pressure PA of a nozzle 10 that is as constant as possible, the quality of the components produced by countercurrent injection is improved due to a more homogeneous mixing of the material components. Furthermore, the flexibility of using such a nozzle 10 is increased, particularly with frequent opening and closing and varying mass flows.

[0062] It should be noted here that all aspects of the invention described above, considered individually and in any combination, and in particular the details shown in the drawings, are claimed to be essential to the invention. The same applies to the described process steps. Modifications to these are familiar to those skilled in the art. Reference symbol list: 1 control unit 2 pressure sensors for material pressure 3 Pressure sensor for collection groove 4 Dosing pump 5 valve 6a Supply line 6b Return line 7 component containers 8 Pressure fluid line 9 Pressure fluid reservoir 10 nozzles 20 nozzle housings 22 Nozzle outlet 23 Piston chamber 24 Material room 25 Pressure fluid chamber 26 Entrance opening 27 Return opening 28 Pressure fluid connection 29 Vent connection 30 Seal 31 Material channel 32 Material throughput 33 Circumferential channel 34 Sealing seat 35 Leadership section 36 Seal 40 jet needle 41 nozzle pins 42 Nozzle opening 50 nozzle block 51 Fasteners 52 Exclusion 53 Seal 54 Pressure fluid inlet 55 Vent opening 60 nozzle pistons 61 material area 62 Pressure fluid area 63 Sealing retaining ring 64 Piston covers 65 screw 66a,b connection channels 67a,b Perimeter recess 68 recording 69 lead 70 Sealing device 71a first sealing element 71b second sealing element 72a,b circumferential groove 73 seals 80 piston space 81 Monitoring opening 82 Collecting 83 Circumferential gap 84 Perimeter inner surface 100 Device for regulating the discharge pressure L Longitudinal axis PM Material Printing PC standard pressure PA discharge pressure

Claims

[1] Nozzle (10) for countercurrent injection of a liquid material for mixing with other components, comprising: - a nozzle housing (20) having at least one inlet opening (26) for supplying a liquid material and a nozzle outlet (22) for discharging the material, - wherein the nozzle housing (20) has a piston chamber (23) extending along a longitudinal axis (L) of the nozzle housing (20); - a nozzle piston (60) which is axially displaceable in the piston chamber (23) along the longitudinal axis (L) and separates a material chamber (24) and a pressure fluid chamber (25) from each other, - wherein a material surface (61) of the nozzle piston (60) can be subjected to a material pressure (PM) of the material and a pressure fluid surface (62) of the nozzle piston (60) can be subjected to a control pressure (PC) of a pressure fluid; - a nozzle needle (40) which is connected to the nozzle piston (60) and forms a variable nozzle opening (42) with the nozzle outlet (22); - a sealing device (70) that seals a circumferential gap (83) between the nozzle housing (20) and the nozzle piston (60), - wherein the control pressure (PC) in the pressure fluid chamber (25) is adjustable to control a discharge pressure (PA) of the material at the exit from the nozzle opening (42), wherein - the sealing device (70) comprises first and second sealing elements (71a, 71b), characterized by , that - the nozzle piston (60) forms a receptacle (68) for the sealing device (70), - the sealing device (70) has a sealing retaining ring (63) with circumferential recesses (67a, 67b) for receiving sealing elements (71a, 71b), - from the material surface (61) at least one connecting channel (66a) between the material chamber (24) and a circumferential recess (67a) and - at least one connecting channel (66b) is formed between the pressure fluid surface (62) and a circumferential recess (67b), - the first and second sealing elements (71a, 71b) are each designed as a sealing ring with a C-profile and a lateral circumferential groove (72a, 72b), - wherein the circumferential groove (72a) of the first sealing element (71a) is oriented towards the material surface (61) and the circumferential groove (72b) of the second sealing element (71b) is oriented towards the pressure fluid surface (62), - wherein the sealing element (71a, 71b) expands in a radial direction when the circumferential groove (72a, 72b) is filled with a pressurized liquid, for example the material or the pressurizing fluid. [2] Nozzle (10) according to claim 1, characterized by, that the first and / or second sealing elements (71a, 71b) comprise PTFE. [3] Nozzle (10) according to one of the preceding claims, characterized by , that a monitoring opening (81) is provided in the nozzle housing (20) to which a pressure sensor (3) can be connected in order to monitor the pressure in a piston space (80) between the first and second sealing elements (71a, 71b). [4] Nozzle (10) according to claim 3, characterized by , that a collecting groove (82) is formed in the nozzle housing (20), which opens into the piston space (80) between the first and second sealing elements (71a, 71b) and is connected to the monitoring opening (81). [5] Nozzle (10) according to one of the preceding claims, characterized by , that the maximum stroke speed of the nozzle piston (60) during operation of the nozzle (10) is between 1 m / s and 15 m / s. [6] Nozzle (10) according to one of the preceding claims, characterized by, that the maximum stroke of the nozzle piston (60) is more than 1.0 mm. [7] Nozzle (10) according to one of the preceding claims, characterized by , that the nozzle needle (40) has a nozzle pin (41) which forms an annular gap with the nozzle outlet (22), wherein the nozzle pin (41) has a diameter between 0.5 mm and 10 mm. [8] Mixing head, especially for countercurrent injection mixing of liquid materials, comprising - a mixing chamber and - at least two nozzles facing each other (10), characterized by , that at least one of the nozzles (10) is designed according to one of claims 1 to 7. [9] Device (100) for controlling the discharge pressure of a material as it exits a nozzle, comprising: - at least one nozzle (10) according to one of claims 1 to 7; - a metering pump (4) which is connected to the nozzle (10) via a supply line (6a) to supply the nozzle (10) with a liquid material; - a pressure fluid reservoir (9) which is connected to the nozzle (10) via a pressure fluid line (8) to supply the nozzle (10) with a pressure fluid; - a valve (5) for adjusting a control pressure (PC) of the pressure fluid in a pressure fluid chamber (25) of the nozzle (10); - a pressure sensor (2) for detecting a material pressure (PM) of the material; - a control unit (1) designed to actuate the valve (5) to adjust the control pressure (PC) based on a pressure deviation of the detected material pressure (PM) from a predetermined target discharge pressure. [10] Method for controlling the discharge pressure of a material at exit from a nozzle (10) according to claims 1 to 7, wherein a slidably mounted nozzle piston (60) of the nozzle (10) separates a material chamber (24) and a pressure fluid chamber (25) from each other and a material surface (61) of the nozzle piston (60) can be subjected to a material pressure (PM) of the material and a pressure fluid surface (62) can be subjected to a control pressure (PC) of a pressure fluid, wherein the method comprises the following steps: - Storing a target discharge pressure with which a material is to be discharged from the nozzle (10) in a control unit (1); - Conveying a material into the material chamber (24) of the nozzle (10) using a metering pump (4); - Detection of material pressure (PM) by a pressure sensor (2); - Transferring the detected material pressure (PM) to the control unit (1); - Determining the pressure deviation of the material pressure (PM) from the predetermined target discharge pressure by the control unit (1); - Setting a control pressure (PC) in the pressure fluid chamber (25) by actuating a valve (5) based on the pressure deviation, preferably at least once during a shot of the nozzle (10). [11] Method according to claim 10, characterized by that the control pressure (PC) is adjusted at least 100 times per second. [12] Method according to any one of claims 10 to 11, characterized by - Closing the nozzle (10) by setting a control pressure (PC) that is higher than the material pressure (PM), and / or - Opening the nozzle (10) by setting a control pressure (PC) that is lower than the material pressure (PM), and / or - Adjusting a nozzle opening (42) of the nozzle (10) for the discharge of the material by setting a control pressure (PC) which is at least substantially the same as the material pressure (PM).

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