3D print head

Abstract

The invention relates to a print head (1) for a pumpable plastic-viscous mixture, for example for 3D concrete printing or 3D mortar printing. The print head (1) comprises: - a mixing chamber (2) having a side wall (21), a feed opening (3) and an outlet (4) designed as a nozzle element (41); - a device for connecting a material conveying hose (31) to the feed opening (3) of the mixing chamber (2); and - at least one injection device (5) having injection nozzles (51) for injecting at least one liquid additive. According to the invention, two or more injection nozzles (51) are arranged on the print head (1) on the side wall (21) of the mixing chamber (2). Furthermore, a plurality of injection nozzles (51) are connected for injection, via a single feed line (52).

Description

[0001] 3D printing head

[0002] The invention relates to a 3D printing head according to the preamble of claim 1.

[0003] In connection with the processing of shotcrete, nozzle systems designed as 3D-printed heads for applying concrete, mortar, or similar materials are already known. If rapid curing of the material to be processed is desired, an additive can be added to the concrete, mortar, or similar material shortly before application, ideally already thoroughly mixed in the nozzle.

[0004] From the document DE 10 2020 003 760 A1, for example, a nozzle designed as a 3D printing head for dispensing concrete or mortar is known, comprising a housing and a mixing chamber made of elastic material arranged therein and delimited by a peripheral wall. The mixing chamber extends along a longitudinal axis at least between an inlet opening and an outlet opening. An actively drivable mixing device in the form of an agitator is arranged in the mixing chamber. A conically tapered discharge opening, through which the concrete or mortar exits the nozzle, is in flow-conducting connection with the outlet opening of the mixing chamber. A cavity extending axially and circumferentially is arranged around the elastic peripheral wall of the mixing chamber and the surrounding housing, which cavity essentially surrounds the mixing chamber in the circumferential direction. The elastic peripheral wall of the mixing chamber can deform into the cavity during operation of the nozzle.In this way, the formation of deposits on the peripheral wall of the mixing chamber is avoided. A nozzle for dispensing, for example, concrete or mortar is also known from the document EP 3431 172 A1. The nozzle has a main opening for supplying the concrete and at least one additional opening for supplying an additive, in particular a setting accelerator, as well as a discharge opening. An actively driven mixer with a mixing tube is provided between the additional opening and the discharge opening. In order to be able to use such a nozzle for 3D printing, the inner diameter of the mixing tube is provided to be a maximum of 8 cm, preferably a maximum of 6 cm, in particular 2-4 cm. It is possible to design the process so that the concrete or mortar begins to harden already in the nozzle. Due to the thin mixing tube, concrete can be dispensed from the nozzle homogeneously, precisely, and with pinpoint accuracy.A valve can be provided between the mixer and the discharge opening to temporarily stop the material flow. Furthermore, the nozzle can have an inlet for compressed air to blow out the concrete, allowing the material discharge to also be operated with compressed air.

[0005] The production and processing of colored concrete are also fundamentally familiar from concrete construction. During the mixing process, a color, in liquid or solid form, is added to the components of the concrete mixture. This coloring process then colors the entire mixture and subsequently processes it.

[0006] In this context, DE 10 2021 121 046 A1 discloses a device for producing structures or objects from colored concrete, which operates quickly, efficiently, and reliably and allows for easy cleaning. The device describes a device for 3D concrete printing with an extruder designed as a 3D printing head and movably attached to a robot arm. The extruder has an inlet and a nozzle outlet, with a conveying channel for a liquid concrete stream located between them. A concrete conveying pump and a concrete conveying hose for supplying the liquid concrete are connected upstream of the extruder. The extruder also has an injection device for injecting a setting accelerator into a mixing tube or mixing chamber for mixing with the liquid concrete stream.In addition, a further injection device is provided for injecting at least one dye into the liquid concrete stream, wherein the injection device for the respective dye is arranged upstream of the injection device of the setting accelerator in the flow direction of the liquid concrete stream.

[0007] The fundamental problem with nozzle systems designed as 3D printing heads is that the additive, which causes the concrete or mortar to harden, can lead to increased deposits forming inside the nozzle. Especially when the flow through the nozzle is temporarily stopped and then resumed, it is particularly important to be able to add the additives precisely and with the finest dosage.

[0008] The object of the present invention is to further develop a 3D printing head with regard to efficiency and reliability.

[0009] This object is achieved by a 3D printing head having the features of independent claim 1. The subclaims relate to advantageous developments and variants of the invention.

[0010] The invention includes a print head for a pumpable plastic-viscous mixture, for example for 3D concrete printing or 3D mortar printing. The print head comprises

[0011] - a mixing chamber with a side wall, a feed opening and an outlet designed as a nozzle element,

[0012] - a device for connecting a material conveying hose to the feed opening of the mixing chamber,

[0013] - at least one injection device with injection nozzles for injecting at least one liquid additive.

[0014] According to the invention, two or more injection nozzles are arranged on the side wall of the mixing chamber on the print head. Furthermore, several injection nozzles are connected to the injection system via a single supply line.

[0015] Preferably, all injection nozzles can also be connected to the injection system via a single supply line. In this case, the supply line can encompass the side wall of the mixing chamber to supply the injection nozzles.

[0016] In this way, the injection nozzles are supplied with liquid additives, such as setting accelerators or color mixtures, from a central supply unit. The central supply unit can also be used to uniformly control the pressure for all injection nozzles at a single level, and to adjust the delivery rate accordingly. An electronic control system and a pneumatic cylinder allow the start of injection, the injection quantity, and the injection process to be precisely controlled. Preferably, the valves do not open and close simultaneously during the injection process, but rather circumferentially around the side wall of the mixing chamber. Typically, at least one valve is always open during operation. It is also planned to adjust the mixing ratio of the liquid additives to the viscous mortar or concrete using a certain number of simultaneously open valves.

[0017] The particular advantage of the invention lies in the special type of injection, which ensures uniform pressure at each nozzle and thus a particularly homogeneous mixing of the plastic-viscous mixture with the liquid additives.

[0018] In a preferred embodiment of the invention, the supply line can be designed as an annular channel on the side wall of the mixing chamber, which supplies the injection nozzles. The annular channel can partially or completely surround the mixing chamber at the side wall. The injection nozzles, which serve to inject at least one liquid additive into the mixing chamber, are then integrated into the annular channel. Geometric conditions in the mixing chamber and the associated material flow of the plastic-viscous mixture can be crucial for the precise design of the annular channel and the positioning of the injection nozzles.

[0019] Advantageously, the side walls of the mixing chamber can be cylindrical and / or conical, and the annular channel of the supply line can be arranged around the circumference of the mixing chamber. In this case, the shape of the mixing chamber makes it essentially rotationally symmetrical about a longitudinal axis, whereby the material flow of the plastic-viscous mixture in the area of ​​the injection nozzles occurs axially along the longitudinal axis. To exploit this symmetry, the annular channel is arranged around the circumference entirely or only in sections to supply the injection nozzles.

[0020] In a further preferred embodiment of the invention, the supply line at the mixing chamber can be designed in a torus shape to supply the injection nozzles. The torus, through which the injection nozzles are supplied, encloses the mixing chamber in a ring-like manner around its circumference. The torus thus forms the annular end of the central supply line into which the injection nozzles are integrated.

[0021] In a preferred embodiment of the invention, several color injection nozzles for injecting a colorant can be connected to the side wall of the mixing chamber via a single color supply line for color injection. In this embodiment, the injection device with injection nozzles for injecting setting accelerator as the first liquid additive comprises color injection nozzles based on the same principle, which are also connected and supplied by another central supply line for color mixtures.

[0022] Alternatively, the injection device with injection nozzles can advantageously additionally comprise a device for injecting a dye. In this embodiment, the setting accelerator and dye components are combined in liquid form and subsequently introduced into the mixing chamber via the injection nozzles.

[0023] Advantageously, the device for injecting a colorant can be connected to the feed line at the mixing chamber. By bringing the liquid additives together in the central feed line early on, sufficient to complete mixing of the additives can be achieved before the mixture enters the mixing chamber via the injection nozzles. This prepares the additives for further blending with the plastic-viscous mixture, such as concrete or mortar, for further homogeneous mixing.

[0024] In a further preferred embodiment of the invention, three or more injection nozzles can be arranged on the side wall of the mixing chamber at equal or unequal spacing from one another. For example, the injection nozzles can be arranged in groups or in pairs. Attachments positioned around the mixing chamber may require the injection nozzles to be arranged at unequal spacing from one another for space reasons. The primary consideration in the arrangement of injection nozzles is the factors that influence the injection characteristics for a homogeneous mixture of the liquid additives with the plastic-viscous mixture in the mixing chamber.

[0025] In a preferred embodiment of the invention, 4, 6, or 8 injection nozzles can be arranged on the side wall of the mixing chamber. An even number of injection nozzles can be a simple and preferred solution for homogeneous mixing, taking into account the symmetry conditions, for example, in cylindrical mixing chambers.

[0026] Advantageously, the injection nozzles can be opened individually or in groups for injection. Individual or grouped control of injection nozzles allows for variable introduction of the liquid additives in terms of quantity, location, and time. Depending on the material flow and the nature of the plastic-viscous mixture in the mixing chamber, precise control of the additive quantities is essential.

[0027] Advantageously, adjacent injection nozzles can be opened sequentially for injection. The temporal sequence can be a circulating addition to the pumpable plastic-viscous mixture around the mixing chamber, which correlates with stirring devices in the mixing chamber.

[0028] In a preferred embodiment of the invention, the injection nozzles can be designed as pneumatic solenoid valves. The valves are actuated, for example, via a double-acting pneumatic cylinder, which in turn is controlled by a solenoid valve. The solenoid valve simultaneously opens and closes a compressed air channel alternately. This pushes the pneumatic cylinder forward or backward. Alternatively, the injection nozzles can also be designed as electrically operated cylinders.

[0029] The injection nozzles can preferably have nozzle needles with which injection openings arranged in the side wall can be opened and closed. In practice, there is a risk that foreign substances, such as mortar or concrete additives, can enter the injection nozzles and cause them to become impermeable to liquid additives. In addition to controlling the injection process, a nozzle needle is suitable for mechanically clearing and cleaning the injection opening. For this purpose, a nozzle needle can also reach through an injection opening into the interior of the mixing chamber and, if necessary, mobilize hardened residues at the injection opening.

[0030] Advantageously, a mixing device rotating around a central axis can be arranged inside the mixing chamber, the rotation of which correlates with the injection of the injection nozzles. A mechanical agitator is also suitable for scraping off material located on the inner wall of the mixing chamber and conveying it further. In a further preferred embodiment of the invention, a mixing element of the mixing device can pass through the respective opened injection nozzle during injection. In this way, the mixing device, designed, for example, as an agitator, and the injection behavior of individual valves can be coordinated. For this purpose, an element of the agitator can pass through the valve opening shortly after the injection of the solidification accelerator.

[0031] Advantageously, a device for cleaning the injection device and / or the mixing chamber can be provided. For this purpose, flushing lines and drain lines are provided to clear the mixing chamber and the injection device of the mixture in the flow. In particular, the hardening material components must be removed from the print head.

[0032] In a further preferred embodiment, the device for cleaning the mixing chamber can be arranged between the side wall and an agitator. For this purpose, injection nozzles extending into the mixing chamber can preferably be arranged in the upper area. The injection nozzles are pressurized with water or another cleaning fluid. For example, the nozzles can open automatically when the water pressure increases and do not require an additional control unit to function. If the water pressure drops, the nozzles close again automatically at a defined minimum pressure. Electronically controlled injection nozzles can also be used for precise dosing and, if necessary, for selecting different cleaning fluids.

[0033] Advantageously, a device for cleaning the mixing chamber can be arranged at the feed opening downstream of the material conveying hose. Since the plastic-viscous mixture emerging from the material conveying hose comes into contact with the liquid additive in the area of ​​the feed opening, it may be advantageous to arrange an additional cleaning device in this area.

[0034] In a preferred embodiment of the invention, a modular agitator can be arranged in the mixing chamber, in which at least mixing blades, spacer rings, and sidewall scrapers are arranged as modules on an agitator shaft. With a modular agitator, the individual modules can be variably selected according to the material flow and ensure particularly homogeneous mixing of the plastic-viscous mixture with the liquid additives. The respective modules are mounted on an agitator shaft and held together with a locking device at the end. Both the agitator shaft and the modules are designed to prevent rotation relative to each other.

[0035] In the following, exemplary embodiments and variants of the invention are explained in more detail with reference to the drawings. They show:

[0036] Figure 1 schematically shows an oblique view of a print head, and

[0037] Figure 2 shows a schematic view of an internal view of an injection nozzle with nozzle needle

[0038] Figure 3 shows a schematic longitudinal section of a print head.

[0039] Figure 1 shows a schematic oblique view of a pressure head 1 for dispensing a pumpable, plastic-viscous mixture, such as concrete, mortar, or the like. The pressure head 1 has a mixing chamber 2 defined by a side wall 21. Arranged inside the mixing chamber 2 is an agitator (not visible in Figure 1) that is rotated by a drive unit 7. In the illustrated embodiment, the mixing chamber 2 is cylindrical.

[0040] A material feed hose 31 for the plastic-viscous mixture is connected to the mixing chamber 2 via a feed opening 3. An outlet 4 in the form of a nozzle element 41 is formed on the mixing chamber 2 in the material flow direction. The curable plastic material exits the printing head 1 via the nozzle element 41 for processing after the mixing chamber 2.

[0041] An injection device 5 with four injection nozzles 51 for injecting liquid additives into the mixing chamber 2 is arranged on the cylindrical side wall 21 of the mixing chamber 2. In the illustrated case, an annular channel 53 is formed around the entire circumference of the cylinder, into which the injection nozzles 51 are integrated. In this case, the annular channel 53 centrally supplies all four injection nozzles 51 and, as a continuation of the supply line 52, serves as the link for supplying the injection nozzles 51 with liquid additives. The injection device 5 also comprises a further supply line as a device 55 for injecting a colorant, which opens into the supply line 52. The liquid additives are, in particular, setting accelerators or color components. A uniform pressure level for each of the injection nozzles 51 is maintained via the central supply line 52 for injection.Flushing lines 6 are arranged as a device for cleaning the injection device 5 and the mixing chamber 2 in order to remove the mixture in the material flow from the mixing chamber 2 and the injection device 5 from the print head 1 at the end of a printing process.

[0042] Figure 2 shows a schematic interior view of an injection nozzle 51 with nozzle needle 54. The nozzle needle 54 is designed so that it can penetrate into an injection opening 22 provided in the side wall 21 and completely seals it. In Figure 2, the nozzle needle 54 is in the open position so that the liquid additive can flow from the annular channel 53 into the mixing chamber 2 via the injection opening 22. To close it, the nozzle needle 54 is moved into the injection opening 22, thus interrupting the liquid flow. Should foreign matter enter the injection opening 22 from the mixing chamber 2, it is removed by the nozzle needle 54 when it is closed. Figure 3 shows a schematic longitudinal section of a print head 1 in the area of ​​the mixing chamber 2. An agitator 8 is arranged inside the cylindrical mixing chamber 2 and is set in rotation by a drive unit 7.

[0043] The cleaning device 61 of the mixing chamber 2 is arranged in the upper area between the side wall 21 and an agitator 8. Preferably, injection nozzles that are pressurized with water are used as the cleaning device 61. The injection nozzles 61 open automatically when the water pressure increases. When the water pressure decreases, the injection nozzles 61 close automatically again.

[0044] A further cleaning device 62 for cleaning the mixing chamber 2 is arranged at the feed opening 3. This part of the print head 1 represents a certain dead space during the cleaning process, which is reliably removed by the further cleaning device 62.

[0045] A modular agitator 8 is arranged in the mixing chamber 2 of the print head 1. The agitator 8 comprises an agitator shaft 81, on which mixing blades 82, spacer rings 84, and sidewall scrapers 83 are arranged. These ensure particularly homogeneous mixing of the plastic-viscous mixture with the liquid additives. The respective modules are mounted on an agitator shaft and held together with a terminal lock nut 85.

[0046] At the outlet 4, the curable plastic material exits the printing head 1 via the nozzle element 41 after the mixing chamber 2 for further processing.

[0047] List of reference symbols

[0048] 1 print head

[0049] 2 mixing chambers

[0050] 21 Side wall

[0051] 22 Injection opening

[0052] 3 Feed opening

[0053] 31 Material conveyor hose

[0054] 4 Outlet

[0055] 41 Nozzle element

[0056] 5 Injection device

[0057] 51 injectors

[0058] 52 supply line

[0059] 53 Ring Canal

[0060] 54 jet needle

[0061] 55 Device for supplying dye

[0062] 6 Flushing line

[0063] 61 Cleaning device mixing chamber, injection nozzle

[0064] 62 Cleaning device feed opening, injection nozzle

[0065] 7 Drive unit

[0066] 8 agitator

[0067] 81 agitator shaft

[0068] 82 mixing blades

[0069] 83 sidewall wipers

[0070] 84 spacer ring

[0071] 85 Lock nut

Claims

Patent claims 1 . Print head (1 ) of a pumpable plastic-viscous mixture, for example for 3D concrete printing or 3D mortar printing, - with a mixing chamber (2) with a side wall (21), a feed opening (3) and an outlet (4) designed as a nozzle element (41), - with a device for connecting a material conveying hose (31) to the feed opening (3) of the mixing chamber (2), - with at least one injection device (5) with injection nozzles (51) for injecting at least one liquid additive, characterized in that - that two or more injection nozzles (51) are arranged on the side wall (21), - that several injection nozzles (51) are connected via a single supply line (52) for injection.

2. Print head (1) according to claim 1, characterized in that on the side wall (21) of the mixing chamber (2) the supply line (52) is designed as an annular channel (53) which supplies the injection nozzles (51).

3. Print head (1) according to claim 2, characterized in that the side wall (21) of the mixing chamber (2) is cylindrical and / or conical and the annular channel (53) of the feed line (52) is arranged over the cylinder circumference of the mixing chamber (2).

4. Print head (1) according to claim 3, characterized in that the supply line (52) on the mixing chamber is designed in a toroidal manner to supply the injection nozzles (51).

5. Print head (1) according to one of claims 1 to 4, characterized in that several ink injection nozzles for injecting a dye are connected to the side wall of the mixing chamber (2) via a single ink supply line for ink injection.

6. Print head (1) according to one of claims 1 to 4, characterized in that the injection device (5) with injection nozzles (51) additionally comprises a device (55) for injecting a dye.

7. Print head (1) according to claim 6, characterized in that the device (55) for injecting a dye opens into the supply line (52) at the mixing chamber (2).

8. Print head (1) according to one of claims 1 to 7, characterized in that three or more injection nozzles (51) are arranged at equal or unequal distances from one another on the side wall (21) of the mixing chamber (2).

9. Print head (1) according to one of claims 1 to 8, characterized in that 4, 6 or 8 injection nozzles (51) are arranged on the side wall (21) of the mixing chamber (2).

10. Print head (1) according to one of claims 1 to 9, characterized in that the injection nozzles (51) can be opened individually or in groups for injection.

11. Print head (1) according to claims 1 to 10, characterized in that adjacent successive injection nozzles (51) can be opened one after the other for injection.

12. Print head (1) according to one of claims 1 to 11, characterized in that the injection nozzles (51) are designed as pneumatic solenoid valves.

13. Print head (1) according to one of claims 1 to 12, characterized in that the injection nozzles (51) have nozzle needles (54) with which injection openings (22) arranged in the side wall (21) can be opened and closed.

14. Print head (1) according to one of claims 1 to 13, characterized in that a mixing device rotating about a central axis is arranged in the interior of the mixing chamber (2), the rotation of which correlates with the injection of the injection nozzles (51).

15. Print head (1) according to claim 14, characterized in that a mixing element of the mixing device passes the respectively opened injection nozzle (51) during the injection.

16. Print head (1) according to one of claims 1 to 15, characterized in that a device for cleaning (6) the injection device (5) and / or the mixing chamber (2) is arranged.

17. Print head (1) according to claim 16, characterized in that the device for cleaning (6, 61) of the mixing chamber (2) is arranged between the side wall (21) and an agitator (8).

18. Print head (1) according to claim 16 or 17, characterized in that a device for cleaning (6) the mixing chamber (2) is arranged at the feed opening (3) downstream of the material conveying hose (31).

19. Print head (1) according to one of claims 1 to 18, characterized in that a modularly constructed agitator (8) is arranged in the mixing chamber (2), in which at least mixing blades (82), spacer rings (82) and side wall wipers (84) are arranged as modules on an agitator shaft (81).

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