CZ2023206A3 - A print head for 3D print of concrete - Google Patents

Abstract

The print head for 3D printing of concrete includes a mixing tube (1), which includes a main inlet opening (2) for the supply of concrete, at least one secondary inlet opening (3) for the supply of an additive, a main outlet opening (4) for the outlet of concrete mixed with an additive, and a mixing device (5) connected to the drive (6), located at least between the secondary inlet opening (3) and the main outlet opening (4), and comprising a rotating shaft (7) on which the mixing elements (9 to 12) are arranged. The mixing device (5) contains at least one first mixing element (9) of the first homogenization zone for homogenizing the mixture of concrete and water at the entrance to the print head, at least one second mixing element (10) of the mixing zone for mixing the mixture of concrete and water with the additive using a horizontal and /or vertical section, at least one third mixing element (11) of the second homogenization zone for additional homogenization of the mixture of concrete, water and additive and/or for slowing down the flow of this mixture, and at least one fourth mixing element (12) of the outlet zone for cleaning the inner surface of the main outlet opening (4) and/or to ensure a homogeneous output of concrete from the main outlet opening (4).

Description

Printhead for 3D concrete printing

The field of technology

This invention relates to a print head for the realization of concrete constructions, buildings and objects made of materials for construction and construction production using additive manufacturing technology (3D concrete printing, "3DCP", "3D concrete printing").

Current state of the art

3D concrete printing is a technology for manufacturing structures, buildings and their parts by layering thin layers of cement mixtures, mortars and concrete. It enables great shape variability, material savings and faster implementation of construction projects. An important part of the technology for the creation of 3D objects from cement mixtures is the print head and its components enabling the modification of the building mixture during the printing process.

In 3D printing of concrete, one-component material is mainly used, where all the components are already prepared in ready-made dry mixtures, to which only water is added during the implementation. The finished wet mixture is then transported to the print head and the print head only serves to regulate the output material.

There is also a technology of adding additives to the concrete mixture before the nozzle itself, but it shows problems of backflow and mixing of additives into the printing mixture. The main solution in this case is a worm feeder (e.g. printhead from the COBOD company) or a simple rod stirrer with low efficiency (e.g. a printhead from the VERTICO company).

The mixing of additives is due to the speed of the reaction of the accelerator with the cement in the printing mixture. The reaction occurs very quickly (on the order of 1 to 2 minutes), so it is necessary to dynamically mix additives into the mixture so that there is no formation of lumps or insufficient homogenization of the mixture, which results in suboptimal concrete strength properties.

European patent application EP 3431172 A1 describes a print head for 3D printing of concrete or mortar, containing a main inlet opening for the supply of concrete or mortar, at least one secondary inlet opening for the supply of additives, a main outlet opening for the outlet of concrete or mortar mixed with an additive (e.g. . with a concrete hydration accelerator (aluminum sulfate)), and a mixing tube containing an actively powered mixing device located between the side inlet and the main outlet. The inner diameter of the mixing tube is a maximum of 8 cm, with an outlet of a maximum of 6 cm, preferably 2 to 4 cm, which enables more accurate dosing of a smaller amount of concrete or mortar for 3D printing needs. The mixing device contains a driven rotary shaft on which mixing elements are placed, especially paddles, wings, zebra or mixing elements with spindle displacement or mixing elements in the shape of a crankshaft, preferably with vertical and longitudinal zebras. The transverse zebra provides intensive mixing of the stream of concrete or mortar in the direction perpendicular to the flow axis, and the longitudinal zebra acts by shearing forces and ensures internal mixing. A pneumatic hose valve can be placed between the mixing device and the main outlet opening for short-term stopping of the flow of pressed concrete or mortar. A three-way injection valve can be placed in the adjacent inlet opening, with the advantage of a needle valve controlled pneumatically (by air pressure), enabling the interruption of contact of the additive with the mixing thickening concrete or mortar, and also enabling flushing with a flushing agent (e.g. water).

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The disadvantages of the above print heads are:

• stirring devices with an unchanging sequence of stirring elements, where the same stirring elements (see Fig. 3 and 6 of EP 3431172 A1) or groups of the same stirring elements (see Fig. 7 and 8 of EP 3431172 A1) are repeated in periods, and thus do not reflect the degree of mixing of concrete or mortar;

• rigidly assembled mixing devices, which can only be replaced as a whole when worn, although different mixing elements have different levels of wear depending on their position in relation to the main and side inlets;

• fixed, non-modular assembly of the mixing chamber, which does not allow changing the length of the mixing zone, the number of additive inputs and the size of individual mixing zones, as well as does not allow changing only the most mechanically exposed part of the mixing chamber;

• pneumatic control of the needle valve for the additive supply, which requires additional pneumatic equipment for handling the additive supply, and which, by mixing air with concrete, leads to its strength degradation.

In Japanese patent application JPH 04269299 A and Japanese patent JP 2566179 B2, a device for preventing clogging of the supply of the hardening agent to the mixing chamber for mixing concrete during tunnel construction is described. The mixing chamber contains the main inlet opening for the supply of concrete, the adjacent inlet opening for the supply of the additive (hardening agent), the main outlet opening for the outlet of concrete mixed with the additive, and a mixing tube containing actively driven mixing devices with mixing elements (blades arranged on a rotating shaft), located between the side inlet and the main outlet. A tube with pressurized air (see Fig. 4 from JP 04269299 A) is located in the adjacent downstream opening, enabling the interruption of contact of the additive with the mixed thickening concrete under the action of the spring in the spring chamber, which indicates the open or closed position of the valve. The disadvantage of the pneumatic control of the adjacent upstream opening is the requirement for additional pneumatic equipment, and the fact that mixing air with concrete leads to its strength degradation. Furthermore, this solution allows the spring chamber to be filled with an additive solution, where it can cause blocking or damage to the spring.

In the Chinese patent application CN 114932609 A, a print head for 3D printing of concrete is described, containing a simple mixing tube containing two two-component mixture feeds, and actively driven mixing devices with mixing elements, which are paddles arranged on a rotating shaft and snaking feeders arranged below them. The disadvantage of the print head is insufficient mixing of both components in the mixing tube.

Czech patent application CZ 2021124 A3 describes a print head including at least two print units spaced apart in the print plane for simultaneous printing in different, mutually offset print planes, whereby each print unit includes an extruder, a filament feeder, a cooling mechanism and a nozzle. The print head can be used for single-component 3D printing of modular building blocks. The disadvantage of the print head is its limitation to single-component mixtures without the possibility of continuous mixing of other components.

The Czech utility model CZ 34847 U1 describes a print head with nozzle rotation for 3D printing of concrete mixtures (e.g. continuous printing of concrete mixture containing aggregate with a maximum grain size of 8 mm and other additives). The print head consists of a body with an inlet opening for the supply of a single-component processed mixture, a screw mechanism for regulating the amount of printed material, and an exit nozzle equipped with a winding mechanism for shaping and applying the processed mixture in the required shape to the substrate. The disadvantage of the print head is its limitation to single-component mixtures without the possibility of continuous mixing of other components.

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In the state of the art, there is a need to provide a variable, modular and structurally simple print head for 3D printing of concrete, which reflects the variability of the degree of concrete mixing, enables the replacement of the most worn elements with modules, and does not require additional equipment to prevent clogging of the additive supply.

The essence of the invention

The aim of the invention is to provide a print head for 3D printing of concrete with a step-by-step and modular mixing device, which simply prevents clogging of the additive feed with mixed concrete. The specified print head is designed so that concrete does not settle in the mixing chamber and the main exit opening (i.e. exit nozzle), so that sufficient and homogeneous mixing of the mixture occurs, even with different viscosities of the input mixture.

In the first aspect of this invention, the said goal is achieved by a print head for 3D printing of concrete, containing a mixing tube, which contains:

a. main supply hole for concrete supply;

b. at least one adjacent feed hole for additive feed;

c. the main exit opening for the exit of concrete mixed with an additive; a

d. mixing device connected to a drive (e.g. an actively driven motor), located at least between the side inlet opening and the main outlet opening, and containing a rotating shaft on which the mixing elements are arranged.

The essence of the mentioned print head lies in the fact that the mixing device contains:

e. at least one first mixing element of the first homogenization zone for homogenizing the mixture of concrete and water at the entrance to the printing head, whereby the first mixing element is arranged on the rotating shaft essentially above the level of the adjacent supply opening;

f. at least one second mixing element of the mixing zone for mixing the mixture of concrete and water with an additive using horizontal and/or vertical shear, whereby the second mixing element is arranged on the rotating shaft essentially at the level of the adjacent supply opening;

Mr. at least one third mixing element of the second homogenization zone for additional homogenization of the mixture of concrete, water and additive and/or for slowing down the flow of this mixture, whereby the third mixing element is arranged on the rotating shaft essentially below the level of the adjacent supply opening; and h. at least one fourth mixing element of the exit zone for cleaning the inner surface of the main exit opening and/or for ensuring a homogeneous exit of concrete from the main exit opening, whereby the fourth mixing element is arranged on the rotating shaft essentially at the level of the main exit opening.

By dividing the mixing device into zones, it makes it possible to reflect the degree of concrete mixing, especially depending on its displacement by the print head in time and on the progress of the hydration reaction of concrete with water and additives. Thorough mixing of additives into the printing mixture is achieved by mixing elements enabling continuous horizontal and vertical mixing, homogenization and reduction of the effect arising from the rotation of non-Newtonian liquids, and at the same time prevents the centrifugation of coarse fractions towards the edge of the mixing tube.

The individual mixing elements can be arranged on the rotating shaft as removable segments or fixed, and further they can be separated by delimiting elements. The removable segments can be replaced as needed (during mechanical exposure to concrete), as different mixing elements have different levels of wear depending on their position in relation to the main and side inlets. Detachable segments also allow changing the length of the mixing zone, the number of adjacent inlets for more additives and the size of the individual mixing zones. The fixed arrangement of the mixing elements, on the other hand, enables the provision of a specific finished product that cannot be further disassembled.

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The first stirring element can be a large zebra, i.e. zebra protruding radially relative to the axis of the rotating shaft. Primary zebras can be arranged in more than one plane (or even in several planes), e.g. four in the shape of a four-pointed star with a hole in the middle for threading the rotating shaft.

The second stirring element can be a C-profile, including two horizontal zebras connected by a longitudinal zebra, i.e. two zebras protruding radially relative to the axis of the rotating shaft, and connected by a zebra running parallel to the axis of the rotating shaft. More C-profiles can be arranged on the rotating shaft, whereby they can differ in the length of the ribs (e.g. shorter lateral zebra and longitudinal zebra in one C-profile and longer lateral zebra and longitudinal zebra in another C-profile). C-profiles protrude radially with respect to the pivot shaft axis in different directions.

The third stirring element can be the first return vane, including a transverse zebra, from which a vane emerges towards the main and side entrance opening (i.e. upward) at a sharp and perpendicular angle to the said transverse zebra.

The third stirring element can also be a second return vane projecting laterally with respect to the rotary shaft (i.e. without a transverse zebra), whereby the surface of said return vane is formed by a plane inclined around an axis perpendicular to the axis of the rotary shaft.

The third stirring element may be a blade further to the brake, including a transverse rib, from which at least one blade protrudes towards the main and secondary inlet openings (i.e. upward) and the main exit opening (i.e. downwards) at an essentially perpendicular angle to said transverse zebra.

The third stirring element can be a circular element protruding laterally with respect to the rotating shaft, i.e. forming a circle in a plane perpendicular to the axis of the rotary shaft.

The third mixing element can also be a large zebra, as was described above for the first mixing element.

The fourth stirring element can be fork cleaners including two transverse zebras, through which a slanting longitudinal zebra (i.e. the tip of the fork itself) emerges from each transverse zebra in the direction of the main outlet opening, with the outlet ending in a point, at such an acute angle with respect to said transverse zebra, that in essence, it copies the inner wall of the main exit opening for rubbing the said inner wall with a diagonal longitudinal zebra. This element ensures the patency of the main exit opening, the uniformity of the print and prevents the exit material from settling in the rest zones of the mixing tube and its gradual build-up.

The fourth stirring element can also be an inverted cone to prevent the concentration of water in the middle of the flow of emerging concrete and to ensure a homogeneous output of concrete from the main exit hole, whereby the surface of the inverted cone can be essentially smooth or it can include a protruding thread guided helically along the said surface, which enables regulate (press or stop) the flow of emerging pressed concrete. The inverted cone can be arranged in the middle of the fork cleaner mentioned above.

A needle valve can be arranged in the adjacent inlet opening to interrupt the contact of the additive with the mixed concrete in the mixing zone. This needle valve contains a valve chamber containing a sliding piston dividing the valve chamber into a spring part and a working part. In the spring part, there is a return spring connected to the sliding piston for moving the sliding piston between the open and closed positions. In the working part there is an inlet of the additive solution and an outlet of the additive solution into the mixing tube (i.e. connected to the mixing chamber), while on the sliding piston there is a needle protruding from the side of the working part in the direction of the outlet of the additive solution to allow the said outlet of the additive solution to remain in in the open position in the presence of overpressure of the additive solution in the working part (ie the needle does not close the outlet of the solution

- 4 CZ 2023 - 206 A3 additive) or to allow the said outlet of the additive solution to be left in the closed position without the presence of the said excess pressure of the additive solution in the working part (ie the needle does not close the outlet of the additive solution). This excess pressure of the additive solution can be advantageously between 1 and 5 · 10 ⁵ Pa, e.g. 1, 2, 3, 4 or 5 · 10 ⁵ Pa, and thus the needle valve is directly and automatically controlled by the pressure of the incoming additive solution, not by additional pneumatic equipment. The mentioned needle valve prevents the settling and gradual filling of the adjacent upstream opening with mixed concrete, as well as the penetration of mechanical impurities in the direction of the needle valve space.

A rod protruding outside the valve chamber can be arranged on the sliding piston from the side of the spring part for manual opening of the additive solution outlet. A seal for liquid-tight separation of the spring and working parts of the valve chamber can be placed on the sliding piston. Slip rings can be placed on the sliding piston to center the position of the sliding piston and the needle relative to the additive solution outlet.

The mixing tube can contain detachable segments, whereby at least one segment has an inner insert to prevent abrasion of the mixing tube with the mixing concrete.

The next supply opening, especially the inlet of the additive solution of the needle valve, can be connected to the pump station for the preparation of the additive solution. The pump station can contain a dosing pump, an additive reservoir, a pump for preparing water for cleaning the print head and an expansion tank. The pump station and additive supply can be controlled by the operator's panel connected to the central control system.

In the second aspect of this invention, the mentioned goal is achieved by a print head for 3D printing of concrete, containing a mixing tube, which contains:

a. the main water hole for the supply of concrete;

b. at least one adjacent inlet opening for additive supply;

c. the main exit opening for the exit of concrete mixed with an additive; a

d. mixing devices connected to a drive (e.g. an actively driven motor), located at least between the side inlet opening and the main exit opening, and containing a rotating shaft on which the mixing elements are arranged.

The essence of the mentioned printing head lies in the fact that a needle valve can be arranged in the adjacent inlet opening to interrupt the contact of the additive with the mixed concrete in the mixing zone. This needle valve contains a valve chamber containing a sliding piston dividing the valve chamber into a spring part and a working part. In the spring part, there is a return spring connected to the sliding piston for moving the sliding piston between the open and closed positions. In the working part there is an inlet of the additive solution and an outlet of the additive solution into the mixing tube (i.e. connected to the mixing chamber), while on the sliding piston there is a needle protruding from the side of the working part in the direction of the outlet of the additive solution to allow the said outlet of the additive solution to remain in in the open position in the presence of overpressure of the additive solution in the working part (i.e. the needle does not close the outlet of the additive solution) or to enable the said outlet of the additive solution to be left in the closed position without the presence of the said overpressure of the additive solution in the working part (i.e. the needle does not close the outlet of the additive solution). This excess pressure of the additive solution can be advantageously between 1 and 5 · 10 ⁵ Pa, e.g. 1, 2, 3, 4 or 5 · 10 ⁵ Pa, and thus the needle valve is directly and automatically controlled by the pressure of the incoming additive solution, not by additional pneumatic equipment. The mentioned needle valve prevents the settlement and gradual growth of the adjacent downstream opening with mixed concrete, as well as the penetration of mechanical impurities in the direction of the needle valve area.

Other optional features of the print head according to the second aspect of this invention are identical to the features of the print head according to the first aspect of this invention.

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In the third aspect of this invention, the aforementioned goal is also achieved by a system for 3D printing of concrete, containing the aforementioned print head. The system may also include a rotary shaft drive (actively driven motor), stirring tube seals for separation and protection of the space with the drive, nozzles for flushing the print head with water or a cleaning solution. The sealing of the mixing tube for separation and protection of the space with the drive prevents the penetration of fine parts of the mixture into the drive mechanism, and can be solved with the help of a set of wiper sleeves (guffers) with a full lubricant, or a mechanical seal or a sealing rope.

The specified print head enables the processing of material with a grain size of 0 to 4 mm, 0 to 8 mm and 0 to 16 mm. These are mainly mortar mixes, concretes, polymer materials.

According to the current state of the art, print heads usually use single-component mortar or concrete mixtures without the addition of additives during the printing process. Building printing heads are usually only a pipe, directing the flow of concrete, or a low-angle device with a gravity-fed auger feeding the material to the exit nozzle. The mentioned print head with direct injection of additives allows the preparation of standard concrete with additional additives injected and mixed in the print head just before the exit from the main exit hole, which allows the modification of the printing mixture during the printing process, as well as the use of wet concrete or mortar mixtures produced from local sources. . An important element is the speed and quality of mixing the additive into the concrete mixture and its sufficient homogenization when passing through the printing head.

The purpose of this invention is to process materials from local sources using free components of concrete, mortar and cement mixtures, their modification according to climatic and production conditions, without the need to use pre-made prefabricated mixtures. Furthermore, the possibility of varying the amount and type of added additives according to the immediate need, thorough mixing of additives, homogenization of the mixture and the possibility of adding other additives according to the conditions necessary for high-quality processing of the mixture.

The specified print head will bring savings in costs, the possibility of modifying the properties of the output material during the process, regulation of the speed of solidification and the rheology of the concrete. It also solves the possibility of discolouration of the concrete mixture during the printing process.

Clarification of drawings

fig. 1 shows a cross-sectional side view of the print head.

fig. 2 shows a detail of the individual zones of the stirring elements of the print head.

fig. 3A and 3B illustrate the print head stirring device.

fig. 4 shows a cross-sectional side view of the inverted cone in the main outlet.

fig. 5A and 5B show a cross-sectional side view of the needle valve.

fig. 6 shows a perspective view of the system for 3D printing of concrete.

fig. 7 shows a side view of the system for 3D printing of concrete.

fig. 8 shows a perspective view of the pumping station.

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Examples of the implementation of the invention

Example 1

One example of implementation is the print head according to fig. 1, containing the mixing tube 1, which contains the main inlet opening 2 for the supply of concrete, two adjacent inlet openings 3 for the supply of the additive (but even one is sufficient for the need to add the additive), the main outlet opening 4 for the outlet of concrete mixed with the additive, and a mixing device 5 located between the main inlet opening 2 and the main exit opening 3, and containing a rotating shaft 7 on which the mixing elements 9 to 12 are arranged. The division of the mixing elements 9 to 12 into individual zones is shown in fig. 2 and the mixing device 5 is shown in fig. 3A and 3B.

According to fig. 1 to 3, the mixing device 5 contains eight (only four visible) first mixing elements 9, the first homogenizing zone for homogenizing the mixture of concrete and water at the entrance to the print head in the form of two groups of four main zebras, respectively. two four-pointed stars after four pointed zebras. The first mixing elements 9 are arranged on the rotating shaft 7 essentially above the level of the adjacent supply opening 3.

According to fig. 1 to 3, the mixing device 5 further contains four (only two visible) second mixing elements 10 mixing zones for mixing the mixture of concrete and water with an additive with the help of horizontal and vertical shear in the form of C-profiles 14 including (each) two transverse zebra connected by a longitudinal zebra . The second mixing elements 10 are arranged on the rotating shaft 7 essentially at the level of the adjacent supply opening 3.

According to fig. 1 to 3, the mixing device 5 further contains two third mixing elements 11 of the second zone for additional homogenization of the homogenizing mixture of concrete, water and additives and/or for slowing down the flow of this mixture. One third stirring element 11 is a second return vane 16 protruding transversely with respect to the rotating shaft 7, whereby the surface of said returning vane 16 is formed by a plane inclined around an axis perpendicular to the axis of the rotating shaft 7. Another third stirring element 11 is a brake vane 17 including a transverse rib, from which at least one brake vane 17 protrudes towards the main and side entrance openings 2, 3 and the main exit opening 4 at an essentially perpendicular angle to the said transverse zebra. Another third stirring element 11 can be the first return vane 15 including a transverse zebra, from which the vane 15 protrudes towards the main and side entrance openings 2, 3 at a sharp and perpendicular angle with respect to said transverse zebra. Another third stirring element 11 can be a circular element 19 protruding laterally with respect to the rotating shaft 7, i.e. forming a circle in a plane perpendicular to the axis of the rotating shaft, and/or a transverse zebra 13, as was described above for the first stirring element 9. The third stirring elements 11 are arranged on the rotating shaft 7 essentially below the level of the adjacent supply opening 3.

According to fig. 2 to 3, the mixing device 5 further contains a fourth mixing element 12 of the exit zone for cleaning the inner surface of the main exit opening 4 and for ensuring a homogeneous exit of concrete from the main exit opening 4 in the form of a cleaning fork 18 including two horizontal zebras, through each horizontal zebra in the direction of the main exit opening 4, a slanting longitudinal zebra emerges, with the exit ending in a point, at such a sharp angle with respect to the mentioned transverse zebra, that it essentially copies the inner wall of the main exit opening 4 for rubbing the said inner wall with a slanting longitudinal zebra. The fourth stirring element 12 is arranged on the rotating shaft 7 essentially at the level of the main outlet opening 4.

According to fig. 4, the mixing device also contains one fourth mixing element 12 of the outlet zone for cleaning the inner surface of the main outlet opening 4 and for ensuring a homogeneous outlet

- 7 CZ 2023 - 206 A3 of concrete from the main exit hole 4 in the form of an inverted cone 20 to prevent the concentration of water in the middle of the flow of the exiting concrete and to ensure a homogeneous exit of concrete from the main exit hole 4, because the surface of the inverted cone 20 is essentially smooth (not shown) in Fig. 5) or includes a protruding thread 21 helically guided along said surface.

Example 2

Another example of implementation is the needle valve 8 for interrupting the contact of the additive with the mixed concrete in the mixing zone according to fig. 5, arranged in the adjacent inlet opening 3 (according to Fig. 1 to 3). The needle valve 8 contains a valve chamber 23 containing a sliding piston 24 dividing the valve chamber 23 into a spring part 25 and a working part 26. In the spring part 25, a return spring 27 connected to the sliding piston 24 is arranged to move the sliding piston 24 between the open and closed positions. In the working part 26, there is an inlet 28 of the additive solution and an outlet 29 of the additive solution into the mixing tube 1. On the sliding piston 24, a needle 30 protruding in the direction of the outlet 29 of the additive solution is arranged on the sliding piston 24 from the side of the working part 26 in order to allow the said outlet 29 of the additive solution to be kept in in the open position in the presence of the overpressure of the additive solution in the working part 26 or to enable the said exit of the additive solution to be left in the closed position without the presence of the said overpressure of the additive solution in the working part 26. A rod 31 protruding outside the valve chamber 23 is arranged on the sliding piston from the side of the spring part 25 for manual opening of said outlet 29 of the additive solution. On the sliding piston 24 is placed a seal 32 for liquid-tight separation of the spring and working parts 25, 26 of the valve chamber 23. On the sliding piston 24 are placed sliding rings 33 for centering the position of the sliding piston 24 and the needle 30 with respect to the outlet 29 of the additive solution. Implementation according to fig. 5A from fig. 5B differs by the position of the inlet 28 of the additive solution, while fig. 5B shows a more compact arrangement.

Example 3

Another example of implementation is the system for 3D printing of concrete according to fig. 6 and 7, containing the aforementioned print head, and further the drive 6 of the rotary shaft 7 (actively driven motor), seals 35 of the rotary shaft 7 for separating and protecting the space with the drive 6 from the mixing tube 1, flushing nozzles 36 of the print head for flushing with water or cleaning solution. The system also includes a pump station for preparing the additive solution, according to fig. 8, connected to the adjacent downstream opening 3, especially the inlet 28 of the additive solution of the needle valve_8. The pump station contains a priming pump 39, an additive reservoir 37, a pump 38 for preparing water for the print head tank and an expansion tank 40. The pump station and the feed 28 of the additive solution can be controlled by an operator panel connected to the central control system.

Industrial usability

The print head described above can be used for multi-component 3D printing of concrete, mortar mixes, cement and cement-free building materials and polymer materials with a grain size of max. 16 mm, preferably max. 8 mm, preferably max. 4 mm.

Claims (15)

1. Print head for 3D printing of concrete, containing a mixing tube (1), which contains: a. main supply hole (2) for concrete supply; b. at least one adjacent inlet opening (3) for additive inlet; c. main outlet hole (4) for the outlet of concrete mixed with an additive; and d. mixing device (5) connected to the drive (6), located at least between the side inlet opening (3) and the main outlet opening (4), and containing a rotating shaft (7), on which the mixing elements (9 to 12) are arranged , characterized by the fact that the mixing device (5) contains: e. at least one first mixing element (9) of the first homogenizing zone for homogenizing the mixture of concrete and water at the entrance to the printing head, whereby the first mixing element (9) is arranged on the rotating shaft (7) essentially above the level of the adjacent supply opening (3) ; f. at least one second mixing element (10) of the mixing zone for mixing the mixture of concrete and water with an additive using horizontal and/or vertical shear, whereby the second mixing element (10) is arranged on the rotating shaft (7) essentially at the level of the adjacent supply opening (3); g. at least one third mixing element (11) of the second homogenization zone for additional homogenization of the mixture of concrete, water and additives and/or for slowing down the flow of this mixture, whereby the third mixing element (11) is arranged on the rotating shaft (7) essentially below the level of the adjacent inlet opening (3); and h. at least one fourth mixing element (12) of the exit zone for cleaning the inner surface of the main exit opening and/or for ensuring a homogeneous exit of concrete from the main exit opening (4), whereby the fourth mixing element (12) is arranged on the rotating shaft (7) essentially at the level of the main exit hole (4). 2. Print head according to claim 1, characterized by the fact that the individual mixing elements (9 to 12) are arranged on the rotating shaft (7) as removable segments or fixed. 3. A print head according to claim 1 or 2, characterized in that the first stirring element (9) is a transverse zebra (13). 4. A print head according to any one of the preceding claims, characterized in that the second stirring element (10) is a C-profile (14), comprising two lateral zebras connected by a longitudinal zebra. 5. Print head according to any one of the preceding claims, characterized in that the third stirring element (11) is a first return vane (15), including a transverse rib, from which a vane protrudes towards the main and side inlet openings (2, 3) (15) at an acute and perpendicular angle with respect to said transverse zebra, and/or a second return vane (16) projecting perpendicularly to the rotating shaft (7), whereby the surface of said return vane (16) is formed by a plane inclined around an axis perpendicular to the axis of the rotating shaft (7). 6. A print head according to any one of the preceding claims, characterized in that the third stirring element (11) is a brake vane (17), including a horizontal zebra, from which towards the main and side inlet openings (2, 3) and the main outlet opening (4) at least one vane protrudes at an essentially right angle with respect to said transverse zebra. 7. A print head according to any of the preceding claims, characterized in that the fourth stirring element (12) is a cleaning fork (18), including two lateral zebras, through which a slanting longitudinal zebra emerges from each vertical zebra towards the main outlet opening (4) , with the outlet ending in a point, at such an acute angle with respect to said transverse zebra, which basically copies the inner wall of the main outlet opening (4) for rubbing said inner wall with a slanted longitudinal zebra. - 9 CZ 2023 - 206 A3 8. A printing head according to any one of the preceding claims, characterized in that the fourth stirring element (12) is an inverted cone (20) to prevent water from concentrating in the middle of the flow of the emerging concrete and to ensure a homogeneous exit of concrete from the main outlet opening (4). whereby the surface of the inverted cone (20) is substantially smooth or includes a protruding thread (21) guided helically along said surface. 9. A printhead according to any of the preceding claims, characterized in that a needle valve (8) is arranged in the adjacent inlet opening (3) for interrupting the contact of the additive with the mixed concrete in the mixing zone, whereby the needle valve (8) contains a valve chamber ( 23) containing a sliding piston (24) dividing the valve chamber into a spring part (25) and a working part (26), whereby in the spring part (25) there is a return spring (27) connected to the sliding piston (24) for moving the sliding piston ( 24) between the open and closed position, and thus in the working part (26) there is an inlet (28) of the additive solution and an outlet (29) of the additive solution into the mixing tube (1), through which on the sliding piston (24) there is from the side of the working parts (26) arranged needle (30) projecting towards the outlet (29) of the additive solution to enable the said outlet (29) of the additive solution to be left in the open position in the presence of overpressure of the additive solution in the working part (26) or to enable the said outlet (29) to be left ) of the additive solution in the closed position without the presence of the indicated overpressure of the additive solution in the working part (26). 10. Printhead according to claim 9, characterized by the fact that on the sliding piston (24) from the side of the spring part (25) a rod (31) protruding outside the valve chamber (23) is arranged for manually opening the said outlet (29) of the additive solution. 11. Printhead according to claim 9 or 10, characterized in that a seal (32) is placed on the sliding piston (24) for liquid-tight separation of the spring part (25) and the working part (26) of the valve chamber (23). 12. Print head according to any one of claims 9 to 11, characterized in that sliding rings (33) are placed on the sliding piston (24) for centering the position of the sliding piston (24) and the needle (30) with respect to the outlet (29) of the solution additives. 13. A print head according to any one of the preceding claims, characterized in that the mixing tube (1) contains detachable segments (34), whereby at least one segment (34) has an internal insert (22) to prevent abrasion of the mixing tube (1) by the mixed concrete . 14. The print head according to any of the preceding claims, characterized in that the adjacent supply opening (3), in particular the inlet (28) of the additive solution of the needle valve (8), is connected to the pump station for the preparation of the additive solution. 15. A system for 3D printing of concrete, characterized by the fact that it includes a print head according to any of the preceding claims.