Technical field

The invention relates to a method for regulating the flow of cement mixture between a pump of the cement mixture and the place of consumption of the cement mixture, in which the cement mixture is transported from the pump to the place of consumption through a transport pipeline.

The invention also relates to a device for transporting cement mixture between the pump of the cement mixture and the place of the cement mixture consumption, comprising a transport pipeline of the cement mixture.

Background art

When creating objects from cement mixture using 3D printing, it is first necessary to produce cement mixture, e.g., using a mixer, and then transport this mixture using a pump to a printing nozzle in a printing head. The printing head is usually located on a robotic arm of a printing device. An additional pump is usually installed in the printing head to precisely control the volume of material flow out of the printing nozzle, or a shut-off valve is installed in the printing head to control the volume of material flow out of the printing nozzle. Controlling the material flow out of the printing nozzle directly by the transport pump in the cement mixture mixer is complicated due to the transport delay caused by a long transport path, usually in the order of tens of meters, between the mixer and the printing head. Therefore, to ensure a smooth supply of the cement mixture to the printing head, it is necessary to solve the problem of fluctuations in volume or in pressure in the pipeline that feeds the cement mixture to the printing head.

Solutions are known, for example according to CN 110181652, CN 210551963 and others, where part of the printing head is a so-called buffer in the form of a small reservoir of cement mixture, to which the mixture is pumped

SUBSTITUTE SHEETS (RULE 26) by a pump from a mixer. The amount of the cement mixture in the buffer is monitored either visually and/or automatically by sensors and, according to this monitoring, the main pump of the cement mixture at the mixer is switched on and off. The disadvantage of this solution is the increase in the weight of the printing head as the auxiliary reservoir in the printing head increases the load on the positioning device of the printing head, usually the robotic arm, which adversely affects not only the dynamics of the 3D printing process, but also the lifetime of the components of the positioning device of the printing head.

CN 106827168 solves a similar problem by installing a return pipeline that feeds excess cement mixture from the printing head back into the mixer. This solution is complicated, requires additional transfer of excess cement mixture back to the mixer and again increases the weight of the printing head, thus increasing the load on the positioning device of the printing head, i.e., on the robotic arm, which reduces the achievable 3D printing dynamics and the lifetime of the device.

CN 111216215 discloses an assembly for 3D printing from cement mixture, comprising two pumps, wherein the second pump is arranged as close as possible to the printing head. This solution further describes the deaeration of the cement mixture by mechanical vibration and by vacuum. The document does not directly describe the regulation of the volume of the cement mixture upstream of the printing head.

The objective of the invention is to remove or at least minimize the disadvantages of the background art, especially to maintain or reduce the weight of the printing head even when using an intermediate reservoir of the cement mixture assigned to the printing head and to maintain or even reduce the load on the positioning device of the printing head, i.e., the robotic arm.

Principle of the invention

The objective of the invention is achieved by a method of regulating the flow of cement mixture between a pump of the cement mixture and the place of consumption of the cement mixture, in which the cement mixture is transported from the pump to the place of consumption by a transport pipeline, whereby the principle of the invention consists in that the internal volume of at least a part of the length of the transport pipeline is changed during the transport of the cement mixture through the transport pipeline depending on the current demand for the cement mixture in the place of consumption of the cement mixture. From a design and utility point of view, it is advantageous if the internal volume of at least a part of the length of the transport pipeline section is changed right before the place of consumption. Preferably, the place of consumption is a printing head of the cement mixture which is adapted for 3D printing of objects from cement mixture.

The principle of the device for transporting the cement mixture between the pump of the cement mixture and the place of consumption of the cement mixture, which comprises a transport pipeline of the cement mixture, consists in that at least a part of the transport pipeline comprises a pipeline section with variable volume adapted to regulate the flow of the cement mixture depending on the current demand for the cement mixture in the place of consumption of the cement mixture.

The pipeline section with variable volume absorbs a certain amount of the cement mixture as the current demand for the cement mixture for 3D printing with a printing head changes. When the immediate need for the cement mixture for 3D printing in the printhead is reduced, the pressure in the supply pipeline of the cement mixture increases, at which point the pipeline section with variable volume begins to increase and accumulates just such an amount of the cement mixture which is supplied to the pipeline by the pump and which is simultaneously not discharged by the printing head in the form of a 3D printed product or the printing is limited to the discharge of a smaller volume of the cement mixture into the 3D printed product. This creates a short-term supply of the cement mixture, a buffer, for further printing after the full discharge of the cement mixture from the printing head to the 3D printed product is resumed, when the pressure of the cement mixture in the transport pipeline decreases again and the cement mixture is supplied from the accumulated amount in the pipeline section with variable volume. If this pipeline section is mounted on the frame of the printing device or is supported by the frame of the printing device, the buffer of the cement mixture does not have to be part of the printing head, which allows to reduce the weight of the printing head, improve the dynamics of the 3D printing process and reduce the load on the positioning device of the printing head, i.e., of the robotic arm.

To eliminate transport delays and to achieve optimal 3D printing dynamics, it is advantageous for the pipeline section with variable volume to be located as close as possible to the printing head.

The pipeline section according to the invention may be implemented, for example, by means of a flexible, expandable element (e.g., a rubber hose) which may be placed inside a rigid pipe. The cement mixture flows through the hose and when the pressure increases, the hose is stretched wide, increasing the internal volume of the hose, which creates a buffer of the cement mixture. When the pressure of the cement mixture decreases, the hose returns to its original cross-sectional size. In this embodiment, air, water or oil can be pressurized between the outer pipe and the inner hose to enable active regulation of the buffer size. The medium then compresses the hose to its original shape and cross-sectional size.

Another possible implementation of the pipeline section according to the invention is the use of telescopic pipes, i.e., at least two pipes inserted into each other. When the pressure of the cement mixture increases and the need to create a buffer of the cement mixture by increasing the volume of the pipeline section, the pipes will slide out of each other, thereby increasing the length of the pipeline and hence the internal volume of this pipeline section . When the pressure of the cement mixture decreases, the pipes slide back into each other, returning the length and internal volume of the pipeline section to its original size. A passive solution for changing the internal volume of the pipeline section uses, for example, springs generating the required initial pressure, while an active solution for changing the internal volume of the pipeline section comprises, for example, a sensor of pressure or force and a suitable active member, for example, an electric drive or a pneumatic or hydraulic cylinder. Description of drawings

The drawings serve to clarify the invention, wherein Fig. 1 shows a complete assembly of a device for 3D printing from cement mixture, Fig. 2. shows the basic principle of the solution according to the invention, i.e., a pipeline section with variable volume capacity, Fig. 3 shows a solution with a flexible pipeline section, inserted into a rigid pipe, the space between the flexible pipeline section and the rigid pipe being filled with a pressure medium, e.g. water, air or hydraulic oil, whereby the pressure of the pressure medium may be measured and regulated by means of a regulating system, Fig. 4. shows an embodiment of the invention using a telescopic pipeline section , the pressure in this section being regulated passively by means of one or more springs connecting the two parts of the telescopic pipeline section and Fig. 5. represents an embodiment of the invention using a telescopic pipeline section, whereby the pressure in this section is regulated actively by means of a sensor, an electronic control system and a suitable actuator.

Examples of embodiment

The invention will be described with reference to exemplary embodiments of a device for 3D printing objects from cement mixture, exemplary embodiments of a supply pipeline of the cement mixture for this device and a method of regulating the flow of the cement mixture between a pump of the cement mixture and the place of consumption of the cement mixture, in which the cement mixture is transported from the pump to the place of consumption through a transport pipeline. The method consists in that the internal volume of at least a part of the length of the transport pipeline section is changed during the transport of the cement mixture through the transport pipeline depending on the current demand for the cement mixture in the place of consumption of the cement mixture. From a design and utility point of view, it is advantageous if the internal volume of at least a part of the length of the transport pipeline section is changed just before the place of consumption, the place of consumption being ideally a printing head of the cement mixture which is adapted for 3D printing of objects from the cement mixture. The device for 3D printing of objects from cement mixture comprises a mixer 1 for preparing the cement mixture. The mixer 1 is coupled by a supply pipeline 2 of the cement mixture to an inlet of a pump 3 of the cement mixture. In an unillustrated exemplary embodiment, the inlet of the pump 3 of the cement mixture is associated with an unloading point of the cement mixture from mobile mixer devices of the cement mixture which is prepared in a different location than the current location of the device for 3D printing objects from the cement mixture, etc.

The pump 3 is coupled with its outlet to the inlet of the transport pipeline 4 of the cement mixture, which is with its outlet of the cement mixture coupled to the inlet of the cement mixture to the printing head 6 for 3D printing of objects from cement mixture. The outlet of the transport pipeline 4 is provided with suitable means to be coupled to the inlet of the cement mixture into the printing head 6 for 3D printing of objects from the cement mixture.

The transport pipeline 4 is provided along at least a part of its length with a pipeline section 5 having a variable internal volume, which forms cement mixture buffer for compensating for possible unevenness of the supply of the cement mixture from the mixer 1 to the printing head 6.

The printing head 6 is adapted for 3D printing of objects from cement mixture by controlled stacking of individual defined layers of the cement mixture on top of each other in a desired plan. The printing head 6 is arranged on a positioning device 22, which is coupled to a control device for controlling the 3D movement of the printing head 6.

According to the exemplary embodiment of Fig. 2, the pipeline section 5 with variable volume is formed by a flexible pipe 10 or hose, which is connected by its inlet 8 to the transport pipeline 4 of the cement mixture. The pipeline section 5 with variable volume is connected by its outlet 9 of the cement mixture to the inlet of the cement mixture to the printing head 6.

In the exemplary embodiment of Fig. 3, the pipeline section 5 with variable internal volume is formed by a combination of the flexible pipe 10 or hose, on the outside of which a rigid pipe 11 is arranged, and wherein the space 12 between the pipes 10, 11 is filled with a pressure medium, for example water, compressed air or hydraulic oil. The rigid pipe 11 is provided with an inlet 13 of the pressure medium. Here, for example, the pressure of the pressure medium in the space 12 is actively regulated according to the current demands of the printing process, e.g., by a sensor 14 connected to a control system 15 and an actuator 16 connected to the pressure medium inlet 17 of the pressure medium.

In an unillustrated exemplary embodiment, the pipeline section 5 with variable internal volume is provided with a general flexible element, including formation of a portion of the pipe wall with a flexible membrane adapted to increase the internal volume of the transport pipeline 4 according to the present invention. In order to protect the general flexible element from damage and to improve the safety of the entire device, it is advantageous if the general flexible element is also arranged at a distance under a rigid cover which forms protection against external damage to the general flexible element and, at the same time, protection for the surroundings of the device in the event of a rupture of the general flexible element, etc.

In the exemplary embodiment of Figs. 4 and 5, the pipeline section 5 with variable internal volume comprises at least one telescopic pipe element, for example a telescopic pipe shown here, which has an outer section 18 and an inner section 19 which are arranged longitudinally inserted into each other, thereby varying the length and therefore also the internal volume of the pipeline section 5 with variable internal volume.

In the exemplary embodiment in Fig. 4, the required initial relative position of the two telescopically arranged parts 18, 19, and therefore also the initial pressure of the cement mixture, is secured by one or more tension springs 20, which are arranged axially with respect to the two parts 18, 19 of the telescopic embodiment of the pipeline section 5 with variable internal volume. This embodiment is an example of passive regulation of the size of the internal volume of the pipeline section 5 with variable internal volume, i.e., an embodiment of passive regulation of the size of the cement mixture buffer for 3D printing. Fig. 5 shows an exemplary embodiment with an embodiment of active regulation of the size of the internal volume of the telescopic pipeline section 5 with variable internal volume, an embodiment of active regulation of the internal volume of the telescopic pipeline section 5 with variable internal volume. In this exemplary embodiment, both parts 18, 19 of the telescopic pipeline section 5 are coupled to the actuator 16 with the sensor 21 of force or pressure, etc., whereby the actuator 16 is connected to the control system 15, to which the sensor 21 of force or pressure is further coupled, etc. The actuator 16 is formed, e.g., by an electric actuator or a hydraulic or pneumatic cylinder, etc.

The device operates in such a manner that the cement mixture is fed through the supply pipe 2 to the pump 3, which supplies the cement mixture through the transport pipeline 4 with the pipeline section 5 with variable internal volume to the 3D printing head 6 of the cement mixture. The 3D printing head 6 deposits defined layers of the cement mixture and forms a printed object 7. The movement of the printing head 6 is ensured by the positioning device 22 on the basis of data supplied by the control system (not shown). When the current demand for the cement mixture for 3D printing in the printing head 6 is reduced, a pressure increase occurs in the cement mixture transport pipeline 4 in which the pipeline section 5 with variable volume starts to increase its internal volume and accumulates just such an amount of the cement mixture which is supplied to the pipeline section 4 by the pump 3 and which is not simultaneously discharged by the printing head 6 into the form of a 3D printed product 7. This creates a short-term supply of the cement mixture, a buffer, in the pipeline section 5 for further printing after the full discharge of the cement mixture from the printing head 6 to the 3D printed product 7 has resumed, when the pressure of the cement mixture in the transport pipeline 4 drops again. After resuming 3D printing, the cement mixture from this buffer is delivered from the accumulated amount in the pipeline section 5 with variable volume, the pressure of the cement mixture in the transport pipeline 4 decreases, and the pipeline section 5 with variable volume reduces its internal volume to its initial value.

The invention is not limited to the solutions explicitly described herein, but is, within the ordinary skills of a person skilled in the art, applicable to other specific embodiments and combinations, including combinations of individual or several embodiments of individual elements of the device and the method which, in the case of printing devices for 3D printing of the cement mixture, make it possible to implement at least one pipeline section 5 with variable volume in the sense of the present invention.

Industrial applicability

The invention can be used, for example, in the construction industry in 3D printing of buildings, etc.

List of references

1 -mixer of cement mixture

2 - supply pipeline of the mixture to the transport pump

3 - transport pump

4 - transport pipeline

5 - buffer

6 - printing head

7 - printed object

8 - inlet of the cement mixture

9 - outlet of the cement mixture

10 - flexible pipe

11 - rigid pipe

12 - space for pressure medium

13 - inlet of pressure medium

14 - sensor of pressure

15 - control system

16 - pressure regulator

17 - pressure medium supply

18 - outer part of the telescopic pipe

19 - inner part of the telescopic pipe

20 - regulation spring

21 - sensor of force

22 - positioning device