NOZZLE FORMING UNIT FOR A REACTION MACHINE AND METHOD FOR MANUFACTURED A PLASTIC PART

Abstract

The invention relates to a nozzle-forming unit (1) for a reaction welding machine. The nozzle-forming unit comprises an inlet channel (2) prepared for connection to a mixing head outlet (11) and a first discharge nozzle (3) prepared for applying a reactive mixture, connected in a first operating state to the inlet channel (2). The invention also provides a second discharge nozzle (4) connected to the inlet channel (2) in a second operating state and also prepared for applying a reactive mixture. Furthermore, the invention relates to a mixing head device for a reaction welding machine comprising said nozzle-forming unit (1), a reaction welding machine comprising the mixing head device (10), and a method for manufacturing a plastic part.

Description

[0001] The invention relates to a nozzle unit (also referred to as a nozzle device or nozzle module) for a reaction injection molding machine (mixing and dispensing several reactive plastic components), comprising an inlet channel prepared for connection to a mixing head outlet and a first discharge nozzle prepared for applying a reactive mixture and connected to the inlet channel in a first operating state. The invention further relates to a mixing head device for a reaction injection molding machine comprising the nozzle unit, the reaction injection molding machine with the mixing head device itself, and a method for producing a plastic part using the reaction injection molding machine.

[0002] Devices and methods of this type are already known from the prior art. DE 10 2004 059 218 A1 discloses a device for producing single- or multi-layer films or compound molded parts containing at least one layer of reactive plastic, comprising storage containers for the reactive components, metering devices for the reactive components, a mixing head, and a spray nozzle.

[0003] US Patent 4,164,187 A discloses a mixing head for reactive liquids, which are continuously fed to the mixing head from separate tanks. The resulting mixture flows continuously through an outlet with a valve that directs the flow to one or more of several dispensing nozzles. Molds are moved synchronously and, in some cases, continuously beneath the nozzles through which the mixture is dispensed.

[0004] DE 1213314 B discloses a multi-component spray gun for liquid synthetic resin, which is equipped with two nozzles that can be connected to two separate containers and a common compressed air source; DE 2536883 A1 discloses a nozzle device for spraying a reaction mixture for the formation of foam, wherein the nozzle has a round distribution chamber into which the mixer opens and which is connected to a number of nozzle outlets directed in different directions to distribute the reaction mixture exiting the nozzle in a predetermined pattern, and wherein the distribution chamber and the various nozzle outlets are connected to each other by nozzle outlet channels that extend from the edge region of the round distribution chamber.

[0005] However, a disadvantage of the nozzle units known from the prior art is that, in order to implement different spray patterns, either the nozzle unit has to be changed or the nozzle unit is relatively complicated to control. With two mixing heads used in parallel, each with its own discharge nozzle, additional switching units are required to convey the reactive mixture and its plastic components to the individual mixing heads.

[0006] It is therefore an object of the present invention to eliminate the disadvantages known from the prior art and in particular to achieve the use of several different nozzles for the production of a plastic part with the lowest possible control complexity.

[0007] According to the invention, this is achieved with a nozzle unit for a reaction casting machine according to claim 1 by providing a second discharge nozzle, which in a second operating state is connected to the inlet channel and is again prepared for applying a reactive mixture. Thus, the two discharge nozzles (first discharge nozzle and second discharge nozzle) can be connected separately and selectively to the inlet channel. Therefore, either only the first discharge nozzle (first operating state) or only the second discharge nozzle (second operating state) is connected to the inlet channel, with a valve device being provided which is configured to switch between the first and the second operating state.

[0008] This results in a nozzle unit in the form of a nozzle exchange module, whereby its discharge nozzles are connected to one and the same mixing head during operation. This significantly simplifies the necessary switching process for redirecting the individual plastic components of the reactive mixture.

[0009] Further advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

[0010] The first discharge nozzle differs from the second discharge nozzle in its nozzle opening cross-section. In this context, it is particularly advantageous if the two discharge nozzles differ in the size / dimension and / or shape of their nozzle opening cross-section. This allows the discharge nozzles to be adapted to specific applications.

[0011] Furthermore, it is advantageous if the first discharge nozzle is designed as a round jet nozzle (preferably with a round, especially preferably circular, or square nozzle opening cross-section) and / or the second discharge nozzle is designed as a flat jet nozzle (preferably with an elliptical or rectangular nozzle opening cross-section).

[0012] In this context, it should be particularly noted that the respective discharge nozzle is always designed to discharge the reactive mixture / reaction mixture, which consists of at least two plastic components, in liquid form. The reactive mixture is preferably a polyurethane material, namely a still-flowable / liquid polyurethane foam / rigid foam. Accordingly, the discharge nozzles are designed to discharge a polyurethane reactive mixture.

[0013] To efficiently control the switching between the two discharge nozzles, a valve assembly (in the nozzle unit) is provided, designed to switch between the first and second operating states. This allows each discharge nozzle to be controlled individually using an OR circuit.

[0014] Furthermore, it is advantageous if the valve assembly is hydraulically actuated / controlled. However, it is also possible in principle to actuate the valve assembly pneumatically or electrically. A combination of hydraulic, pneumatic, and electrical actuation is also preferred.

[0015] Regarding the valve assembly, it is also advantageous if it has a piston with two (separate) connecting channels, the piston being designed such that in a first valve position it connects the inlet channel to the first discharge nozzle via its first connecting channel (transmitting the first operating state), and in a second valve position it connects the inlet channel to the second discharge nozzle via its second connecting channel (transmitting the second operating state). This results in a particularly compact valve assembly.

[0016] It is even more preferred if each connecting channel is designed as a (single) bore. This further reduces the manufacturing effort of the piston.

[0017] The piston is preferably designed as a sliding piston or as a rotary piston.

[0018] If the piston is designed as a sliding piston (i.e., displaceable in an axial direction), it is advantageous if it is guided displaceably within a housing of the nozzle unit by means of a first longitudinal section containing the connecting channels. The sliding piston can then be moved back and forth with particular precision in its longitudinal direction between the individual valve positions.

[0019] In this context, it is also advantageous if the sliding piston has a widened head in a second longitudinal area, to which an adjusting force that forces the valve positions is applied / can be applied during operation.

[0020] It is also advantageous if the piston (preferably axially) has a first recess between the two connecting channels that receives or is designed to receive a sealing material, preferably in the form of an annular groove. This ensures the sealing of the two connecting channels relative to each other.

[0021] In this context, it is also advantageous if the piston has a second recess, preferably designed as an annular groove, on a side of the first connecting channel facing away from the second (preferably axial) side of the first connecting channel, which receives or is designed to receive a sealing material, and / or if it has a third recess, preferably designed as an annular groove, on a side of the second connecting channel facing away from the first (preferably axial) side of the second connecting channel, which receives or is designed to receive a sealing material. This also ensures the sealing of the connecting channels to the environment.

[0022] The sealing material is pre-installed as a seal, preferably a sealing ring, during the assembly of the nozzle unit. Alternatively or additionally, a portion of the reactive mixture that penetrates the respective recess during operation of the nozzle unit also forms the sealing material. In these cases, the connecting channels are always reliably sealed to the environment and relative to each other.

[0023] The invention also relates to a mixing head device for a reaction casting machine, comprising a mixing head having a mixing chamber and a mixing head outlet connected or connectable to this mixing chamber, as well as the inventive nozzle unit attached to the mixing head in a removable manner according to at least one of the embodiments described above, wherein the inlet channel is connected to the mixing head outlet.

[0024] Furthermore, the invention relates to a reaction casting machine with this mixing head device.

[0025] Furthermore, the invention relates to a method according to claim 9 for producing a plastic part, wherein a reactive mixture is applied, using the mixing head device or the reaction casting machine according to the embodiments described above, to a mold defining the geometry of the plastic part or to a blank that already partially forms the plastic part, which is, for example, designed as a dimensionally stable blank or as a film. This allows the plastic part to be produced particularly efficiently as a finished plastic component or as a semi-finished product.

[0026] In other words, only one nozzle change module (one nozzle unit) is used in a mixing head. This module switches between a flat jet and a round jet nozzle. The switching units known from the prior art are therefore no longer required. Thus, according to the invention, a method and a device for manufacturing plastic parts using a mixing head with a nozzle change module are implemented.

[0027] The invention will now be explained in more detail below with reference to a figure, in which context a preferred embodiment is described.

[0028] It shows the only Fig. 1a sectional view of a nozzle unit according to the invention, attached to a mixing head of a reaction casting machine, wherein the section is such that in particular an inlet channel, the outlet channels formed by two discharge nozzles and the connecting channels of the nozzle unit connecting the outlet channels with the inlet channel in a respective valve position of a valve device are recognizable.

[0029] The figure is purely schematic and serves solely to illustrate the invention. The same elements are identified by the same reference symbols.

[0030] The Fig. 1Figure 1 illustrates a unit, hereinafter referred to as a mixing head device 10, consisting of a mixing head 16 and a nozzle unit 1. The mixing head device 10 is used in operation within a reaction injection molding machine, which is not shown in detail here for the sake of clarity. The reaction injection molding machine is typically designed for the production and dispensing / application of a reactive mixture / reaction mixture. The reactive mixture is a polymer reactive mixture composed of various (at least two) reactive polymer components. The at least two polymer components, which are preferably processed and conveyed by the reaction injection molding machine to form the reactive mixture, are polymer components suitable for the production of a polyurethane mixture (polyurethane foam / rigid polyurethane foam).A first plastic component is preferably a dialcohol / diol or a polyol, and a second plastic component is preferably a polyisocyanate. The reaction casting machine or the mixing head device 10 is used to produce a finished plastic part / plastic component or to coat a blank intended for the formation of a plastic part, such as a film (semi-finished product).

[0031] During operation, the two plastic components are mixed in the mixing head 16 in a typical manner to form the reactive mixture. The two plastic components are mixed in a mixing chamber 15 of the mixing head 16. The mixing chamber 15 is located within the mixing head 16, i.e., within a mixing head housing 19. Two side channels 20a and 20b, each carrying one of the plastic components during operation, open laterally into the central mixing chamber 15. Thus, during operation, the plastic components are fed into the mixing chamber 15 via the side channels 20a and 20b. A mixing head outlet 11, exiting the mixing head housing 19, connects to the mixing chamber 15. During operation, the reactive mixture is conveyed from the mixing chamber 15 to the mixing head outlet 11. The mixing head outlet 11 is designed as an outlet bore.

[0032] The modular nozzle unit 1 is detachably attached to the mixing head housing 19 by means of a screw connection, which is not shown here for clarity. The nozzle unit 1 is connected to the mixing head outlet 11. In particular, the nozzle unit 1 has an inlet channel 2 which is connected to the mixing head outlet 11.

[0033] The inlet channel 2 of the nozzle unit 1 is located in a housing 9 of the nozzle unit 1 and is implemented as a bore. The inlet channel 2 penetrates the housing 9 from an outside to an inside. Thus, the inlet channel 2 connects the mixing head outlet 11 to an inside of the housing 9 during operation. A piston receiving chamber 21 is formed on the inside of the housing 9. A piston in the form of a sliding piston 8 of a valve assembly 5 is movably / slidably received in the piston receiving chamber 21. The piston receiving chamber 21 is therefore enclosed by the housing 9 and is essentially cylindrical. The sliding piston 8 has a first longitudinal section 12 which has a substantially constant outer diameter along its length and is therefore essentially cylindrical.The sliding piston 8 (with its first longitudinal section 12) is guided slidably in the piston receiving chamber 21 via a sliding guide. The dimensions of the sliding piston 8 and the piston receiving chamber 21 are coordinated such that there is the narrowest possible gap between the sliding piston 8 and the piston receiving chamber 21 in order to achieve the most precise guidance possible of the sliding piston 8.

[0034] Two connecting channels 6 and 7 extend transversely to a longitudinal axis 22 of the sliding piston 8 and penetrate the sliding piston 8 transversely to the longitudinal axis 22. The two connecting channels 6 and 7 are spaced apart from each other in the axial direction of the longitudinal axis 22 / of the sliding piston 8. The two connecting channels 6 and 7 are angled towards each other at the same angle relative to a reference plane to which the longitudinal axis 22 is defined as a normal. The connecting channels 6 and 7 are essentially identical in design. Both connecting channels 6 and 7 are implemented as bores / through bores penetrating the sliding piston 8 in the transverse direction.

[0035] The housing 9 also contains two connecting passages 23a and 23b, each connected to a discharge nozzle 3, 4, corresponding to the connecting channels 6 and 7. Passages 23a and 23b are also separate from each other and spaced apart axially along the longitudinal axis 22. Like the inlet channel 2, each passage 23a and 23b penetrates the housing 9 radially with respect to the longitudinal axis 22. Depending on the displacement position of the sliding piston 8, each passage 23a and 23b is connected to one of the connecting channels 6, 7 and, via this connecting channel 6, 7, to the inlet channel 2. A discharge nozzle 3, 4 is mounted on the outside of the housing 9 in the area of ​​the exiting passages 23a and 23b. A first discharge nozzle 3 (with a first discharge channel 17 formed by it) is arranged such that it ( / the first discharge channel 17) is connected to the first passage 23a.A second discharge nozzle 4 is arranged adjacent to the first discharge nozzle 3 (with a second discharge channel 18 formed by it) such that it (the second discharge channel 18) is connected to the second passage 23b.

[0036] The sliding piston 8, with its connecting channels 6, 7, is such that it is matched to the inlet channel 2 and to the passages 23a and 23b in a first valve position (as in Fig. 1 (shown) in a first operating state, connects the inlet channel 2 with the first passage 23a and thus again with the first discharge nozzle 3 via its first connecting channel 6, and in a second valve position (axially offset relative to the first valve position) in a second operating state, connects the inlet channel 2 via its second connecting channel 7 with the second passage 23b and thus again with the second discharge nozzle 4.

[0037] Thus, according to the invention, the nozzle unit 1 is implemented as an interchangeable unit that selectively connects either a first discharge nozzle 3 (in the first valve position) or a second discharge nozzle 4 (in the second valve position) to the inlet channel 2. A valve assembly 5, designed as a changeover valve, is provided for switching the nozzle unit 1. The nozzle unit 1 is therefore implemented as a nozzle changer module.

[0038] The first discharge nozzle 3 has a different nozzle opening cross-section than the second discharge nozzle 4. Specifically, the first discharge nozzle 3 is designed as a round jet nozzle, and the second discharge nozzle 4 is designed as a flat jet nozzle. Thus, the two discharge nozzles differ in the shape of their nozzle opening cross-section.

[0039] Furthermore, it is from Fig. 1It is evident that the valve assembly 5 is hydraulically actuated in principle. For this purpose, an actuating device 24 is connected to / provided in a second longitudinal section 13 of the sliding piston 8, which is offset from the first longitudinal section 12. The sliding piston 8 has a head 25 in the second longitudinal section 13, which is located outside the piston receiving chamber 21 and is wider than that of the first longitudinal section 12. Two hydraulic connections 26a and 26b interact with the head 25, through which an actuating force acting axially on the head 25 can each be generated. Thus, depending on the pressure difference between the two hydraulic connections 26a and 26b, either the side of the head 25 facing the longitudinal section 12 or the side facing away from the longitudinal section 12 is pressurized, so that the sliding piston 8 is forced into the respective valve position.

[0040] Furthermore, in Fig. 1It can be seen that a recess 14a to 14c is provided between the two connecting channels 6 and 7, as well as on their opposing axial sides. These recesses serve to seal the connecting channels 6 and 7 from each other and from the environment. The respective recesses 14a to 14c are identically designed as annular grooves. A sealing material is introduced into each recess 14a to 14c during operation. In principle, the sealing material can already be introduced into the sliding piston 8 during pre-assembly of the nozzle unit 1. Additionally or alternatively, each recess 14a to 14c can also be filled with the reactive mixture after the initial commissioning of the nozzle unit 1. The reactive mixture entering the recess 14a, 14b, 14c then hardens and swells to such an extent that it also directly serves as a sealing material. The connecting channels 6 and 7 are therefore effectively sealed.A first recess 14a is arranged axially between the connecting channels 6 and 7 and seals the connecting channels 6 and 7 from each other. A second recess 14b is arranged towards an axial side of the first connecting channel 6 facing away from the second connecting channel 7. A third recess 14c is arranged towards an axial side of the second connecting channel 7 facing away from the first connecting channel 6. Thus, the sealing materials introduced in the second and third recesses 14b and 14c seal the connecting channels 6 and 7 from the environment.

[0041] Furthermore, in Fig. 1A schematically depicted cleaning device 27 can be seen. The cleaning device 27 is part of the nozzle unit 1. The cleaning device 27 has a transverse bore 29 and a check valve 28 inserted into this transverse bore 29. The transverse bore 29 runs transversely to the inlet channel 2 and opens into it. After the reactive mixture has been conveyed through the respective outlet nozzle 3, 4, and thus after a plastic part has been produced or after a blank intended for the formation of a plastic part has been coated with the reaction mixture, air or a cleaning fluid is typically introduced into this transverse bore 29 so that the channels 2, 6 or 2, 7, as well as the passage 23a or 23b including the discharge nozzle 3 or 4, are cleaned / flushed.

[0042] In other words, according to the invention, a mixing head 16 is provided in which an automatic nozzle change between a round jet nozzle and a flat jet nozzle 3, 4 takes place. This avoids the need for complex switching units. The nozzle changing unit 1 according to the invention incorporates a hydraulically driven switching piston (sliding piston 8) for switching between the round and flat jet nozzles 3, 4. The switching piston 8 has two bores (connecting channels 6, 7): one bore (first connecting channel 6) for the round jet nozzle 3 and one bore (second connecting channel 7) for the flat jet nozzle 4. To seal the switching piston 8 externally, the clearance between the switching piston 8 and the housing 9 is relatively small. Furthermore, the switching piston 8 has three small grooves (recesses 14a, 14b, 14c) which are filled with sealing material. Reference symbol list

[0043] 1 Nozzle unit 2 Inlet channel 3 First discharge nozzle 4 Second discharge nozzle 5 Valve assembly 6 First connecting channel 7 Second connecting channel 8 Sliding piston 9 Housing 10 Mixing head assembly 11 Mixing head outlet 12 First longitudinal section 13 Second longitudinal section 14 First recess 14b Second recess 14c Third recess 15 Mixing chamber 16 Mixing head 17 First outlet channel 18 Second outlet channel 19 Mixing head housing 20 First side channel 20b Second side channel 21 Piston receiving chamber 22 Longitudinal axis 23 First passage 23b Second passage 24 Actuating device 25 Head 26 First hydraulic connection 26b Second hydraulic connection 27 Cleaning device 28 Check valve 29 Transverse bore

Claims

1. A nozzle unit (1) for a reaction moulding machine, comprising an inlet channel (2) prepared for connection to a mixing head outlet (11) and comprising a first dispensing nozzle (3), which is prepared for applying a reactive mixture and which is connected to the inlet channel (2) in a first operating state, characterized in that a second dispensing nozzle (4) is present, which is connected to the inlet channel (2) in a second operating state and which is likewise prepared for applying a reactive mixture, in a nozzle opening cross-section differing from the first dispensing nozzle (3), so that the first dispensing nozzle (3) and the second dispensing nozzle (4) are able to be connected separately optionally to the inlet channel (2), wherein the first dispensing nozzle (3) is configured, in the first operating state, to be connected to the inlet channel (2), and the second dispensing nozzle (4) is configured, in the second operating state, to be connected to the inlet channel (2), wherein a valve arrangement (5) is present, which is configured to switch between the first operating state and the second operating state.

2. The nozzle unit (1) according to Claim 1, characterized in that the first dispensing nozzle (3) is configured as a round jet nozzle and / or the second dispensing nozzle (4) is configured as a flat jet nozzle.

3. The nozzle unit (1) according to one of the preceding claims, characterized in that the valve arrangement (5) has a piston (8) having two connecting channels (6, 7), wherein the piston (8) is configured so that in a first valve position it connects the inlet channel (2) via its first connecting channel (6) with the first dispensing nozzle (3), and in a second valve position it connects the inlet channel (2) via its second connecting channel (7) with the second dispensing nozzle (4).

4. The nozzle unit (1) according to Claim 3, characterized in that the piston (8) is configured as a sliding piston and with a first longitudinal region (12), having the connecting channels (6, 7), is guided displaceably in a housing (9) of the nozzle unit (1).

5. The nozzle unit (1) according to Claim 3 or 4, characterized in that the piston (8) has, between the two connecting channels (6, 7), a first recess (14a) receiving a sealing material or configured to receive the sealing material.

6. The nozzle unit (1) according to one of Claims 3 to 5, characterized in that the piston (8) has towards a side of the first connecting channel (6) facing away from the second connecting channel (7), a second recess (14b) receiving a sealing material or configured to receive the sealing material and / or has, towards a side of the second connecting channel (7) facing away from the first connecting channel (6), a third recess (14c) receiving a sealing material or configured to receive the sealing material.

7. A mixing head device (10) for a reaction moulding machine, with a mixing head (16) having a mixing chamber (15) and a mixing head outlet (11) connected or connectable with this mixing chamber (15), and a nozzle unit (1) arranged on the mixing head (16) so as to be removable again, according to one of Claims 1 to 6, wherein the inlet channel (2) is connected to the mixing head outlet (11).

8. A reaction moulding machine with a mixing head device (10) according to Claim 7.

9. A method for producing a plastic part, wherein a reactive mixture, with the use of the reaction moulding machine according to Claim 8, is applied onto a negative mould providing a geometry of the plastic part, or onto a blank already partially forming the plastic part.