Injection device and method for injecting at least two reactive components into a forming tool, and forming machine

Abstract

Injection device (1) for injecting at least two reactive components (A, B) into a mold (2) of a molding machine (20), with - a first injection unit (14a) having a first movable dispensing device (11a) for dispensing a first reactive component (A), - a second injection unit (14b) having a second movable dispensing device (11b) for dispensing a second reactive component (B), - a mixing region (4) which has a first inlet (4a) for the first reactive component (A) and a second inlet (4b) for the second reactive component (B), wherein the reactive components (A, B) are miscible in the mixing region (4), - a first closure element (15a) by which the first entrance (4a) can be closed, - a second closure element (15b) by which the second entrance (4b) can be closed, - a control or regulating unit (16) for outputting control signals at least to at least one of the dispensing devices (11a, 11b) and to at least one of the closure elements (15a, 15b), characterized in that the control or regulating unit (16) has a checking device (17) or is connected to a checking device (17), wherein the control or regulating unit (16) terminates the dispensing movements of both dispensing devices (11a, 11b) as a function of the checking device (17) as soon as both closure elements (15a, 15b) are closed.

Description

[0001] The invention relates to an injection device for injecting at least two reactive components into a shaping tool of a shaping machine, comprising a first injection unit having a first movable dispensing device for dispensing a first reactive component, a second injection unit having a second movable dispensing device for dispensing a second reactive component, a mixing region having a first inlet for the first reactive component and a second inlet for the second reactive component, wherein the reactive components are mixable in the mixing region, a first closure element by which the first inlet can be closed, a second closure element by which the second inlet can be closed, and a control or regulating unit for outputting control signals at least to at least one of the dispensing devices and to at least one of the closure elements.Furthermore, the invention relates to a molding machine with such an injection device, as well as a corresponding method.

[0002] Various processes have been established for the processing of multi-component reactive systems for the series production of plastic and fiber-reinforced plastic composite components. The dosing and mixing processes used are briefly explained below: The state of the art in polyurethane and epoxy resin processing is represented by both low-pressure and high-pressure resin injection processes. In these processes, the components, stored in liquid form in heated day tanks, are pumped or piston-operated to a mixing head, where they are mixed, and the resulting mixture is poured into a mold.

[0003] For caprolactam processing, the solid processing method advocated in AT 515 952 A1 is the method of choice. Here, the granular or flake-like reactive components are first liquefied in a melting unit and collected in a melt zone. Separated from this melting unit, an injection piston is located for each component. From these injection pistons, the melts are then fed via flexible heated hoses into a mixing head, where they are mixed, and the resulting mixture is poured into a mold.

[0004] Common to the dosing and reactive processes described above is the fact that the reactive components must be homogeneously mixed before being introduced into the cavity. The difficulty of the mixing task for a specific material system depends on the required mixing ratio and the required mixing quality.

[0005] This mixing process is particularly challenging when the substances to be mixed differ significantly in their physical or chemical properties, for example, due to significantly different densities, polarities, or viscosity. Furthermore, very different mixing partners also tend to exhibit a pronounced tendency to separate.

[0006] Regardless of the mixing partners to be processed, systems with fillers and the resulting high viscosity, but also mixing partners with very low viscosity, lead to challenges in mixing and processing.

[0007] Depending on the processing method and material, various design approaches have been proposed to ensure an efficient and reliable mixing process.

[0008] For example, static mixers or mixing elements are often used in low-pressure injection processes, as well as in adhesive or foaming technology. These are very inexpensive, quick to replace, and therefore ideal for simple mixing tasks.

[0009] However, if high energy is required to mix the components, or if the mixing must be carried out very quickly due to the desired cycle times and the high reactivity of the mixing partners, high-pressure countercurrent injection is often the method of choice. Here, the components to be mixed are pumped at high pressure (up to 200 bar) through nozzles with a small cross-section (0.1 - 2 mm). As they exit the injection nozzles, the components are greatly accelerated by the release of pressure. The jets of both components therefore collide with high kinetic energy in a mixing chamber, ensuring particularly efficient mixing. This mixing principle is commonly used, for example, in the high-pressure resin injection process.

[0010] Despite the extensive optimization of mixing technology, the systems known to experts or available on the market have various disadvantages.

[0011] Although static mixing elements are replaceable and very inexpensive, self-cleaning systems are usually preferred for series production to achieve appropriate cycle times and minimize the effort required to clean or replace the mixers. A further disadvantage is the fact that a certain material flow rate must initially be maintained to achieve a satisfactory mixing effect. The first material combined in the mixer is therefore usually not optimally mixed and therefore waste. Highly reactive systems, in particular, are very difficult to process with static mixers.

[0012] As already mentioned, high-pressure countercurrent injection is particularly well-suited for mixing in systems requiring increased mixing energy. However, high-pressure countercurrent mixing heads reach their limits when pressures exceeding 50 bar are to be achieved in the molding tool. A common error in such process conditions is so-called cross-foaming: Cross-foaming is defined by experts as the forced recirculation of material already mixed in the mixing chamber into the injection nozzles, the supply lines, or the recirculation lines leading from the mixing head to the tank.

[0013] Certain small quantities are certainly tolerated and are usually diluted by recirculating the components in the respective daily container to such an extent that there is no noticeable impact on the further product quality.

[0014] However, particularly when using caprolactam as a reactive system, there is a significant chemical difference compared to the more commonly used polyurethane or epoxy resin systems. If cross-foaming occurs during component production, this difference manifests itself as follows: The reactive mixture is initially highly diluted because it is flushed into a line containing only one component. When polyurethanes or epoxy resins are used, the respective reactive end groups then react by polyaddition, resulting in a barely noticeable increase in viscosity, since a simple addition reaction does not result in any significant elongation of the molecular chains. The anionic polymerization of caprolactam, on the other hand, is mechanistically speaking a polymerization. Once initiated by appropriate additives, the reaction proceeds with chain growth until a termination reaction occurs.The reaction can therefore proceed until the reactants in the pipes harden, or the material in the day tank is noticeably damaged by recirculation of the reactive mixture.

[0015] DE 32 38 258 C2 therefore proposes a design solution specifically for the processing of caprolactam by modifying the geometry of the discharge valve with additional recesses. While this prevents direct cross-foaming when the nozzles are arranged opposite each other, such modifications have no effect on the possible entry of already mixed material from the mixing chamber into the nozzle bores.

[0016] Further prior art is known, for example, from DE 10 2005 051 205 A1, AT 517 390 A1, EP 3 243 639 B1 and JP 2006- 35 845 A.

[0017] The object of the present invention is therefore to eliminate the problems known in the prior art. In particular, the aim is to prevent backflow of material in the mixing area into the feed lines.

[0018] This is achieved by an injection device having the features of claim 1, a molding machine having the features of claim 9, and a method having the features of claim 10. Accordingly, the invention provides that the control or regulating unit comprises or is connected to a checking device, wherein the control or regulating unit, depending on the checking device, preferably by issuing a switching signal, terminates the dispensing movements of both dispensing pistons as soon as both closure elements are closed. Thus, the pressure triggered by the dispensing movement prevents material from flowing back into the supply lines despite this pressurization.

[0019] In principle, there are several ways to ensure that the termination of the dispensing movements is only triggered when the locking elements are actually closed.

[0020] According to a first variant, closing signals can be output to the closure elements from the control or regulating unit, and a delay time, preferably determined empirically, is stored in a storage medium of the control or regulating unit. The checking device outputs the switching signal to terminate the deployment movements after the stored delay time has elapsed following the output of the closing signals. This delay time is set so that, based on experience, it is sufficient for safe closing.

[0021] Alternatively (or additionally), each closure element can be provided with a closure sensor that is signal-linked to the monitoring device to monitor the closed position of the closure element. The monitoring device then outputs the switching signal to terminate the dispensing movements as soon as a closure signal is received from both closure sensors. These closure sensors can be specifically designed as limit switches located in the area of ​​the nozzles or inlets. These limit switches can also be located in the area of ​​the drives, for example, at the rear of the nozzle. If the closure elements are hydraulically actuated, the evaluation of the stop pressure can also be used to detect when the closed position has actually been reached and to output the corresponding signal to the control or regulating unit.

[0022] The reactive components are preferably produced from solid precursors, which are melted in the injection units. Such solid precursors for polymer production are preferably additive-containing mixtures of ε-caprolactam or laurolactam, precursors of thermoplastic epoxy resins, or crosslinking silicones.

[0023] The solid precursors may contain additives, in particular for initiating and accelerating the reaction, regulating the chain length and the degree of branching, stabilizing the resulting polymers or crosslinked end products (UV protection, flame retardants, antioxidants), functional additives, colors and chromophores, fillers, crystallization aids and nucleating agents, modifiers to improve mechanical properties, in particular impact strength, coupling agents to support a possible fiber / matrix bond, removing disruptive moisture or other low-molecular substances, demolding aids.

[0024] It is also possible to introduce a textile reinforcement or generally to introduce fibers and / or fillers separately into one or more cavities of the forming tool.

[0025] The injection of the individual molten precursors can be carried out with a constant volume flow, constant pressure, a specified pressure or volume profile, or intermittently.

[0026] Protection is also sought for a forming machine with a clamping unit including a forming tool and an injection device according to the invention.

[0027] In a method for injecting at least two reactive components into a forming tool of a forming machine, the object underlying the invention is achieved by the steps of checking whether both closure elements are closed and ending the dispensing movements of both dispensing devices only when both closure elements are closed.

[0028] Further details and advantages of the present invention will be explained in more detail with reference to the description of the figures and the exemplary embodiments presented below. In these, the following figures show: Fig. 1 schematically shows a molding machine with a clamping unit and an injection device, Fig. 2 schematically shows the mixing area with closed entrances, Fig. 3 schematically shows the mixing area with open entrances Fig. 4 to 7 schematically show further variants of closure elements and Fig. 8 to 10 diagrams of the pressure, piston position and control signal curves during one cycle.

[0029] In Fig. 1 shows an exemplary molding machine 20 for producing molded parts, in particular fiber-reinforced plastic components. The molding machine 20 has, on the one hand, the injection device 1 shown on the right and the clamping unit 21 shown on the left. The molding tool 2 consists of a first mold half 2a and a second mold half 2b. The molding tool is clamped on two mold clamping platens 12 and 13 that can be moved relative to one another. An insert 3 (can also be referred to as a semi-finished product) in the form of a preform has already been inserted into the open molding tool 2. For controlling or regulating the molding machine 20, a control or regulating unit 16 is provided, which is also connected to an operating unit 18 (including screen and keyboard) as a human-machine interface. Control lines to the clamping unit 21 and to the injection device 1 are shown as examples.

[0030] The injection device 1 (also called reactive unit) with two injection units 14a and 14b provides the two additive-containing lactam melts (component A and component B) for further processing, which are fed via feed lines 8a, 8b to a mixing area 4. The movement of the dispensing devices 11a and 11b, designed as injection pistons, can be carried out by electric or hydraulic drives (not shown).

[0031] A pressure sensor 9a, 9b is arranged in each injection unit 14a, 14b to measure the media pressure in the piston antechamber. A pressure sensor 5 can also be arranged on the tool side. Alternatively or additionally, pressure measurement can also be performed in the supply lines 8a and 8b.

[0032] The mixing unit used (mixing area 4) can be a conventional high-pressure countercurrent mixing head. Fig. 2 and Fig. 3 shows a preferred embodiment of this mixing area 4. The material flows are introduced into a chamber of the mixing area 4 via preferably nozzle-shaped inlets 4a and 4b. These inlets 4a and 4b can be closed using actively actuated closure elements 15a and 15b, e.g. needle valves. After the reactive components have been mixed in the mixing area 4, the reactive mixture M is passed further into the cavity. The movement of the closure elements 15a and 15b can be controlled electrically, hydraulically or pneumatically, or can be spring-actuated. In addition, closure sensors 7a and 7b (e.g. in the form of inductive proximity switches) can be arranged in the area of ​​the closure element drives (not shown in detail), with which the closed position of the closure elements 15a and 15b in the area of ​​the inlets 4a and 4b is detected.

[0033] In principle, the closure elements 15a and 15b can be completely separate, with independent switching signals S close It is also possible, however, for the closure elements 15a and 15b to be controlled in the form of an electronic coupling. This means, for example, that only the first closure element 15a is directly controlled by a control or regulating unit 16. The second closure element 15b is then controlled dependently on the first closure element 15a. Fig. 4 and Fig. 5, a mechanical coupling is shown. The two closure elements 15a and 15b are coupled via a schematically illustrated coupling device 22. The opening and closing of the inputs 4a and 4b is therefore always synchronous. This is also the case in the embodiment according to Fig. 6 and Fig. 7. Accordingly, there is only one closure device 23 for both entrances 4a and 4b. This closure device 23 is formed by a carrier 24 and the closure elements 15a and 15b formed thereon. In other words, the corresponding surface areas of the carrier 24 form the closure elements 15a and 15b. The carrier 24 thus serves to jointly move the closure elements 15a and 15b formed by the surfaces of the carrier 24 facing the entrances 4a and 4b.

[0034] As already described, the greatest challenges in processing multi-component reactive systems are, among other things, their process-safe mixing.

[0035] The design approaches described above, familiar to those skilled in the art, are certainly applicable to various reactive systems. However, especially for low-viscosity media, a process-based solution is considered significantly more efficient, which is why the present invention addresses this problem through process control and not (only) through the design of the mixing head.

[0036] The solution for eliminating transverse foaming processes is based on the consideration that already mixed reactive material in the area of ​​the closure elements 15a and 15b or from the mixing area 4 can only flow back towards the dosing line if the pressure prevailing there is lower than in the cavity. To achieve this, a liquid flow of the components towards the cavity must be ensured in every operating state in which the closure elements 15a and 15b are open. This can be achieved by an injection process adapted to the switching process of the closure elements 15a and 15b. Specifically, at the end of the injection process, the movement of the dispensing device 11a and 11b is only stopped when the closure elements 15a and 15b are securely closed.

[0037] An example procedure is given with reference to Fig. 1 is explained below. The control or regulating unit 16 generates a switching signal S based on a stored sequence program. close to close the inputs 4a and 4b to the closure elements 15a and 15b. With the output of this switching signal S close the checking device 17 begins to check whether the inputs 4a and 4b are actually closed by the closure elements 15a and 15b. According to a first variant, the checking device 17 uses a delay time t3 stored in the storage medium 19 of the control or regulating unit 16. As soon as the predetermined delay time t3 has elapsed after the output of the switching signal S close has expired, the control or regulating unit 16 sends the switching signal S end-inj to terminate the deployment movements of the deployment devices 11a and 11b. According to a second variant, the checking device 17 waits for the arrival of a closure signal Vclosed of closure sensors 7a and 7b, which (indirectly) monitor the closed position of the closure element 15a and 15b at the respective input 4a and 4b. As soon as this closure signal V closed the checking device 17, the switching signal S is sent by the control or regulating unit 16 - if necessary taking into account an additional short waiting time t4 or t5 end-inj to terminate the spreading movements of the spreading devices 11a and 11b.

[0038] The diagrams in the Fig. Figures 8 to 10 show how various values ​​change along a time axis during an injection cycle. P denotes the injection pressure, preferably measured in the piston pre-chamber. The dotted line shows the piston position K. The control signal of the closure element 15a and 15b is denoted by S. close and S openThe shutter signal measured by the shutter sensors 7a and 7b is denoted by V closed or V opened In Fig. 10, D denotes the hydraulic pressure of the nozzle control (closure elements 15a and 15b).

[0039] An advantageous injection cycle for a two-component reactive system is Fig. 8. After dosing both injection units 14a and 14b, the injection or piston movement begins with the opening of the closure elements 15a and 15b at the mixing area 4. The piston movement can occur at a constant axial movement speed or be preselected using a profile that can be set on the user control (operating unit 18). At the end of the injection, the closure elements 15a and 15b are triggered to close, with the piston movement only stopping at the point in time at which the closure elements 15a and 15b are securely closed.

[0040] According to one variant, this is achieved by the operator being able to set a delay time t3 on the control unit 18 of the control or regulating unit 16. This delay time t3 corresponds at least to the time period between the signal to close the closure elements 15a and 15b and the termination of the injection by stopping the dispensing movement. This delay time can particularly preferably be 2 - 200 ms. This setting is made by the operator using empirically determined test values. (Alternatives to the empirical procedure are described in the Fig. 9 and Fig. 10 described and shown).

[0041] As an alternative to injection with a constant axial movement speed or based on an adjustable speed profile, the injection can also be performed under pressure control: In this case, the injection speed is adjusted based on a preset pressure or a pressure profile. This allows for better adaptation to any thickness changes or inserts in the cavity.

[0042] In a further embodiment, the injection process can also be carried out under pressure control by changing the passage cross-section of the inlets 4a and 4b through the closure elements 15a and 15b during the injection at a constant axial movement speed or based on an adjustable speed profile in order to achieve a predetermined pressure or pressure profile. The change in the passage cross-section can be achieved, for example, by changing the position of a nozzle needle or nozzle tip.

[0043] In a preferred embodiment, the delay time t3 can be different for both injection units 14a and 14b. For example, different line lengths or friction conditions of the dispensing devices 11a and 11b and / or the closure elements 15a and 15b can be compensated for in this way.

[0044] The actual termination of the injection can occur after reaching a preset volume and one or more preset pressures. The criterion reached first leads to the termination of the injection.

[0045] In particular, it may be useful to monitor the media pressure at various positions using appropriate sensors. The media pressure in the piston antechamber of the injection units 14a and 14b is monitored by sensors 9a and 9b. Additionally or alternatively, the pressure in the supply lines 8a and 8b of components A and B can be measured. The cavity pressure can also be measured via a sensor 5.

[0046] After the injection is complete, compression relief of the two pistons can be initiated. This can be position-controlled, but is preferably pressure-controlled, so that a defined target pressure P1 is reached.

[0047] After the injection is complete and before compression release, a waiting time t4 can optionally be set. To monitor the tightness of the system or the service life of machine components, it can be particularly advantageous to cyclically measure the respective pressure drop during this waiting time t4 and compare it with a tolerance stored in the control system.

[0048] In a preferred embodiment of the invention, after dosing and before the start of the injection, the material in the antechamber of the dispensing devices 11a and 11b, designed as injection pistons, or in the supply media lines is first compressed by axial piston movement until a preset pressure P2 is reached. The speed of the piston movement can also be a constant axial movement speed or based on a profile adjustable on the user control. In particular, this ensures that during the injection, even the material that first exits the mixing area 4 is already mixed with the required mixing pressure.

[0049] In a further embodiment of the invention, different target pressures and axial movement speeds can be set for both injection units 14a and 14b in order to be able to react to any inhomogeneity in the material.

[0050] To monitor the tightness of the system or the service life of machine elements, it can be particularly advantageous to cyclically monitor both the necessary path and / or the time required to reach the desired pressure and to compare it with a tolerance stored in the control or regulating unit 16.

[0051] Following the compression of the material described above, a waiting period t1 of 0.1 to 10 seconds, preferably 0.5 to 3 seconds, can optionally be inserted before the start of the injection. To monitor the tightness of the system or the service life of machine elements, it can be particularly advantageous to cyclically monitor the respective pressure drop during this waiting period t1 and compare it with a tolerance stored in the control system. In other words, the pressure curve during the waiting period t1 can be compared from cycle to cycle in order to check the tightness of the respective closure element 15a, 15b or to detect any leaks. A pressure test is therefore carried out.

[0052] Preferably, an adjustable delay time t2 is also implemented with the start of the injection. This specifies the difference by which the piston movement is offset, i.e., earlier or later, than the movement of the respective closure elements 15a and 15b. This setting serves to compensate for the different switching times for the start of the movement of the dispensing device 11a or 11b and the closure element 15a or 15b.

[0053] In a further embodiment of the invention, this delay time t2 can be set separately for both dispensing devices 11a and 11b in order to be able to compensate for any deviations (e.g. caused by friction, signal propagation times, different cable lengths, etc.) by appropriate adjustment on the control.

[0054] An alternative embodiment of the invention is based on the use of closure elements 15a and 15b with travel monitoring or limit switches (see sensors 7a and 7b) for position monitoring. Such a case is shown in Fig. 9 is illustrated using limit switch signals: If one of the criteria for terminating the injection (see above) is reached, the closure of the closure elements 15a or 15b is triggered. If these are closed according to the limit switches (or position monitoring), the piston movement can be stopped immediately. Preferably, however, an adjustable delay time t5 starts. After this delay time t5 has elapsed, the piston movement is also stopped. This delay time t5 is preferably between 2 and 25 ms.

[0055] Another alternative design variant is based on the use of hydraulically controlled closure elements. One such case is Fig.Figure 9 illustrates: If one of the criteria for terminating the injection (see above) is met, the closure of the closure elements 15a and 15b is initially triggered. The hydraulic pressure D is monitored. If an adjustable threshold of the hydraulic pressure D is reached, an adjustable delay time t6 begins. After this delay time t6 has elapsed, the piston movement is also terminated. This delay time t6 is preferably 2 to 25 ms. List of reference symbols: 1 injection device 2 mold tool 2a first mold half 2b second mold half 3 insert 4 Mixing area 4a first entrance 4b second entrance 5 Pressure sensor in the forming tool 7a, 7b shutter sensors 8a, 8b Supply line for component A or B 9 Pressure sensor in the piston antechamber 11a, 11b Dispensing device 12 first mold clamping plate 13 second mold clamping plate 14a Injection unit for component A 14b Injection unit for component B 15a, 15b Closure elements 16 Control or regulating unit 17 Checking device 18 Control unit 19 Storage medium 20 forming machines 21 Locking unit 22 Coupling device 23 Locking device 24 carriers A, B reactive components S switching signal t1 Waiting time before starting injection (“pressure test”) t2 adjustable delay time before injection start t3 delay time t4, t5 waiting time P injection pressure P1 target pressure P2 preset pressure D Hydraulic pressure V shutter signal S Switching signal (for locking elements and for dispensing piston) M reactive mixture

Claims

[1] Injection device (1) for injecting at least two reactive components (A, B) into a mold (2) of a molding machine (20), with - a first injection unit (14a) having a first movable dispensing device (11a) for dispensing a first reactive component (A), - a second injection unit (14b) having a second movable dispensing device (11b) for dispensing a second reactive component (B), - a mixing region (4) which has a first inlet (4a) for the first reactive component (A) and a second inlet (4b) for the second reactive component (B), wherein the reactive components (A, B) are miscible in the mixing region (4), - a first closure element (15a) by which the first entrance (4a) can be closed, - a second closure element (15b) by which the second entrance (4b) can be closed, - a control or regulating unit (16) for outputting control signals to at least one of the dispensing devices (11a, 11b) and to at least one of the closure elements (15a, 15b), characterized by that the control or regulating unit (16) has a checking device (17) or is connected to a checking device (17), wherein the control or regulating unit (16) terminates the dispensing movements of both dispensing devices (11a, 11b) as a function of the checking device (17) as soon as both closure elements (15a, 15b) are closed. [2] Injection device according to claim 1, characterized by that switching signals (S end-inj ) can be issued to end the application movements. [3] Injection device according to claim 1 or 2, characterized by that the control or regulating unit (16) sends closing signals (S close ) can be output to the closure elements (15a, 15b). [4] Injection device according to claim 3, characterized by that a delay time (t3), preferably determined empirically, is stored in a storage medium (19) of the control or regulating unit (16), wherein the output of the switching signal (S end-inj ) to terminate the application movements after the stored delay time (t3) has elapsed after the closing signals (S apse ) has expired. [5] Injection device according to one of claims 1 to 3, characterized by that each closure element (15a, 15b) has a closure sensor (7a, 7b) which is in signal-technical connection with the checking device (17) for monitoring the closed position of the closure element (15a, 15b), wherein the checking device (17) outputs the switching signal (S end-inj ) to terminate the spreading movements as soon as a closure signal (V closed) has been received. [6] Injection device according to one of claims 1 to 5, characterized by that the first drive device (11a) and / or the second dispensing device (11b) is / are designed as a piston, pump or conveyor screw. [7] Injection device according to one of claims 1 to 6, characterized by that the first closure element (15a) and the second closure element (15b) are electronically or mechanically coupled. [8] Injection device according to one of claims 1 to 7, characterized by that the closure elements (15a, 15b) can be driven electrically, hydraulically or pneumatically. [9] Forming machine (20) with a closing unit (21) and an injection device (1) according to one of claims 1 to 8. [10] Method for injecting at least two reactive components (A, B) into a forming tool (2) of a forming machine (20), comprising the steps - dispensing a first reactive component (A) via a first movable dispensing device (11a) of a first injection unit (14a), - dispensing a second reactive component (B) via a second movable dispensing device (11b) of a second injection unit (14b), - Mixing the first reactive component (A) and the second reactive component (B) in a mixing area (4) which has a first inlet (4a) for the first reactive component (A) and a second inlet (4b) for the second reactive component (B), - closing the first entrance (4a) by a first closure element (15a), - closing the second entrance (4b) by a second closure element (15b), characterized by the steps - Check whether both locking elements (15a, 15b) are closed, and - Terminating the dispensing movements of both dispensing devices (11a, 11b) only when both closure elements (15a, 15b) are closed. [11] Method according to claim 10, characterized by that, with closed closure elements (15a, 15b), the reactive components (A, B) are compressed to a specific pressure (P2) in an anteroom of the respective injection units (14a, 14b) and in supply lines (8a, 8b) before dispensing. [12] Method according to claim 11, characterized by that the specific pressure (P2) in the anteroom is achieved by moving the respective dispensing device (11a, 11b) until the specific pressure (P2) is reached, preferably at a constant speed or on the basis of a stored movement profile. [13] Method according to claim 11 or 12, characterized bythat after the compression of the components (A, B) in the respective anteroom of the injection units (14a, 14b) a waiting time (t1) of 0.1 to 10 seconds, preferably of 0.5 to 3 seconds, is waited. [14] Method according to claim 13, characterized by that the pressure (P2) in the respective anteroom of the injection units (14a, 14b) is detected by pressure sensors (9a, 9b). [15] Method according to claim 14, characterized by that the pressure (P2) measured by the pressure sensors (9a, 9b) in the anteroom of the injection units (14a, 14b) is compared with a stored tolerance value during the waiting time (t1), wherein when the tolerance value is reached or undershot, a signal is output, preferably representing insufficient tightness. [16] Method according to one of claims 10 to 15, characterized bythat the dispensing devices (11a, 11b) are controlled offset from the closure elements (15a, 15b) by a delay time (t2) which can preferably be individually adjusted for each dispensing device (11a, 11b). [17] Method according to one of claims 10 to 16, characterized by that after the components (A, B) have been dispensed and before compression relief, an adjustable waiting time (t4) is waited for. [18] Method according to claim 17, characterized by that a pressure measured in the respective injection unit (14a, 14b) during this adjustable waiting time (t4) is compared with a stored tolerance value, wherein when the tolerance value is reached or undershot, a signal is output, preferably representing insufficient tightness. [19] Method according to one of claims 10 to 18, characterized bythat the application devices (11a, 11b) of the injection units (14a, 14b) are controlled on the basis of different movement and pressure profiles, wherein [20] Method according to one of claims 10 to 19, characterized by that the path and / or the time until a desired pressure is reached in one of the injection units (14a, 14b), in supply lines (8a, 8b) and / or in the mixing area (4) is cyclically monitored and compared with a stored tolerance value, a corresponding signal being output when the tolerance value is reached or undershot.

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