A fibre dosing unit, a system for three-dimensional printing and a method of introducing fibres
Patent Information
- Authority / Receiving Office
- AU · AU
- Patent Type
- Applications
- Current Assignee / Owner
- ZAVHY COLLECTIVE BV
- Filing Date
- 2024-12-12
- Publication Date
- 2026-07-16
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
TITLE A fibre dosing unit, a system for three-dimensional printing and a method of introducing fibresTECHNICAL FIELD
[0001] The present invention relates to a fibre dosing unit for introducing fibres to a print head of a system for three-dimensional printing of a structure with a fibre- reinforced mixture. The present invention further relates to a system for three- dimensional printing of a structure with a fibre-reinforced mixture, and to a method of introducing fibres with a fibre dosing unit to a system for three-dimensional printing of a structure with a fibre-reinforced mixture.BACKGROUND
[0002] Sustainability and digitisation are becoming more and more important challenges and spearheads within European and global policies. In addition to zero emissions and circularity, reducing raw material consumption is a priority within the various objectives and digitisation is necessary to keep national or regional economies - in all sectors - competitive in the world. Digitisation for a smarter and more efficient society and industry includes the use of ICT, Al, robotisation and other digital control of processes and products.
[0003] Conventional products, such as concrete structures like parts of bridges or buildings, are made with formwork and are reinforced with steel reinforcement bars. The construction process from design to realization has many steps in which many mistakes can be made because there is still a lot of (human) handicrafts. The design should be translated into a mould, and in the mould the reinforcement should be applied, then the reinforcement should remain in the right place during casting.
[0004] Many materials that are used in the manufacturing of large structures, like buildings or bridges, like concrete, can handle a lot of pressure, but are relatively brittle and therefore, have little pulling force. To prevent cracking and improve its tensile strength and ductility, it is therefore important to reinforce such materials with rebar.
[0005] Three-dimensional printing, like three-dimensional concrete printing (3DCP), can be used much more in the infrastructure, construction, and design industries, where almost every project requires customization of advanced designs with multiple functionalities. The challenges of this industry with regard to sustainability and productivity with 3DCP can also be addressed. The rapid development in 3DCP comes as no surprise, as concrete is the most widely used construction and construction material worldwide. Due to the wide range of functionalities such as strength, durability, fire resistance and the high use in the global construction sector, the use of concrete as a three-dimensional printed material makes it very attractive for the construction sector. Furthermore, the advantages offered by 3DCP to reduce the overall concrete usage makes 3DCP technology a highly attractive solution to address the issues related to sustainability in the building and construction industry.
[0006] Though 3DCP technology offers a more efficient solution for concrete construction, the conventional method of applying steel reinforcement to 3DCP structures is not efficient and, in some cases, not possible. Hence the application of 3DCP technology for the construction industry is limited and not yet strong enough for large-scaled structural applications. An alternative to reinforcing concrete with rebars is by strengthening the concrete with small metallic fibres such as steel fibres and non- metallic fibres such as hemp fibres, basalt fibres, polypropylene fibres, glass fibres etc. However, with the current 3DCP setups used in the industry only small micro fibres can be introduced to the printed concrete. These fibres are used to prevent shrinkage in the concrete rather than structural application related to improving ductility and tensile strength.
[0007] The reinforcing fibres can be added to the mixture that is used to 3D print the structure in various ways. However, controlled dosing of the fibres to the mixture, such as a concrete mixture, may be required to obtain a good-quality fibre-reinforced mixture that can be used for 3D printing of the building structure having the required strength.
[0008] There are various possibilities to apply such fibres in three-dimensional printed construction mixtures. Of all the alternatives explored by knowledge institutions, only a few have shown potentially good results.
[0009] Existing dry mortar pumping systems used for the 3DCP process, based on screw dosing systems, can provide in the dosing of small quantities of micro fibres, which are premixed with the dry mortar, in accurate amounts. The biggest limitation, however, of such a system is that (part of) the fibres, especially large-scale macro fibres - which are crucial for improving material properties - may not be able to pass through the current pumping system for 3DCP. The pump, hose or screw or screw opening then becomes clogged by the fibres resulting in complete stoppage of the material pumping process leading to maintenance work like repairing or replacing parts of the system.
[0010] Another option is to sprinkle fibres during the 3D printing process between each layer. This system is easier to implement in the printing system. However, proper control of the system is difficult, and the quality of the printed output is not homogeneous when using various fibres and / or other ingredients in the printing mixture.
[0011] Therefore, there exists a need for a solution to dosing reinforcing fibres to a print head of a system for three-dimensional (3D) printing of a structure, such as a concrete structure, in a well-controlled manner that solves one or more of the above- mentioned problems.OBJECTIVE
[0012] It is therefore an object of the invention to provide for a fibre dosing unit for introducing fibres to a print head of a system for three-dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture.SUMMARY
[0013] The foregoing object is achieved according to a first aspect of the present invention that relates to a fibre dosing unit for introducing fibres to a print head of asystem for three-dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, said fibre dosing unit comprising: a drum arranged for rotating around a rotation axis and arranged for storing said fibres, provided in bulk to said drum, said drum comprising: one or more collector means attached to an inner wall of said drum and arranged for transporting a portion of said fibres upwards for discharging said portion of said fibres at or near an inner top side of said drum; a transportation means, positioned at least partially inside said drum and below said inner top side for collecting discharged portions of said fibres on said transportation means; wherein said transportation means are arranged to transport fibres collected on said transportation means into: a fibre dosing chamber comprising: a receiving portion at a top side of said fibre dosing chamber and arranged for receiving said fibres from said transportation means, a discharging portion at a bottom side of said fibre dosing chamber and arranged for discharging said fibres from said fibre dosing chamber, an actuator arranged for manipulating said discharging portion between a closed position and an open position; a control unit for controlling said actuator, a speed of transportation of said fibres on said transportation means, and a speed of rotation of said drum, wherein said control unit is further arranged for receiving a value of a weight of said fibres in said fibre dosing chamber, received from: sensor means arranged for measuring said weight of said fibres in said fibre dosing chamber, wherein said control unit is arranged to control said speed of transportation of said fibres on said transportation means and said speed of rotation of said drum in accordance with a predefined fibre dosing rate, defined by said weight of said fibres in said fibre dosing chamber exceeding a predefined threshold weight value, and a predefined constant time interval of manipulating said discharging portion between said closed position and said open position.
[0014] The fibre dosing unit according to the invention provides more control of dosing of the fibres to the system for 3D printing of structures, for example, but not limited to,concrete structures. The fibre dosing unit enables the dosing of fibres in a stepwise (or: discrete) manner that approaches continuous dosing. In this way, precision dosing, including precise dosing of small quantities of fibres, is possible resulting in a more homogeneous distribution of the fibres in the mixture can be obtained. In the present disclosure, with “small quantities” is meant dosing quantities of fibres in the range of from 1 to 500 g / min.
[0015] The fibres may be dosed directly to a print head of the system for 3D printing of structures, but it may also be dosed to a particle transport system or means that transports the fibres to said print head, for example through a hose.
[0016] Furthermore, the configuration of the fibre dosing unit prevents clogging of parts of the unit by too many fibres being discharged too fast from the bulk of fibres in the drum.
[0017] To control the amount of fibres being dropped from the dosing chamber, the speed of transportation of the fibres on the transportation means and / or the speed of rotation of the drum can be adjusted. The time interval of the dosing fibres from the dosing chamber to, for example, a print head of the system for 3D printing of structures, is kept the same.
[0018] In the present disclosure, with "in bulk" means that the fibres are stored in a relatively large quantity in the drum. Thus, without packaging the fibres into individual units, for example for immediate use.
[0019] A second aspect of the present invention relates to a system for three- dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, comprising a fibre dosing unit according to the first aspect of the present invention.
[0020] A third aspect of the present invention relates to a method of introducing fibres with a fibre dosing unit according to the first aspect of the present invention to a printhead of a system for three-dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, said method comprising the steps of: providing said fibres in bulk to said drum; transporting, with said one or more collector means attached to said inner wall of said drum, said portion of said fibres upwards for discharging said portion of said fibres at or near said inner top side of said drum; collecting, with said transportation means, discharged portions of said fibres on said transportation means; transporting, with said transportation means, fibres collected on said transportation means to said fibre dosing chamber; discharging, by manipulating with said actuator said discharging portion from said closed position to said open position, fibres from said fibre dosing chamber; measuring, with said sensor means, said weight of said fibres in said fibre dosing chamber; controlling, with said control unit, said speed of transportation of said fibres on said transportation means and said speed of rotation of said drum.
[0021] A fourth aspect of the present invention relates to a computer program product, comprising a data storage device storing computer program code arranged for performing a method according to the third aspect of the present invention, when said computer program code are loaded onto a memory of an electronic processing unit when executed by said electronic processing unit.
[0022] Corresponding embodiments disclosed below for the first aspect are also applicable for the system for three-dimensional printing (second aspect), the method of introducing fibres (third aspect) and the computer program product (fourth aspect) according to the present invention, unless stated otherwise.DETAILED DESCRIPTION OF THE EMBODIMENTS
[0023] The present fibre dosing unit is elucidated below with a detailed description.
[0024] The fibre dosing unit according to the present invention can be used in any kind of system that is suitable for three-dimensional (3D) printing of structures usingmaterials that may require reinforcing fibres, but the fibre dosing unit is especially suitable for a system for 3D printing of concrete structures with a fibre-reinforced concrete mixture.
[0025] The fibre dosing unit allows the dosing of different types of fibres, such as thick, thin, long, smooth, rough, hooked end, corrugated, circular and / or organic or inorganic, metallic, or virgin or recycled fibres. The fibres may have a length in the range of from 5 mm to 70 mm, preferably from 10 mm to 35 mm, more preferably from 15 mm to 30 mm. Furthermore, the fibres may have a diameter of in the range of from 20 micrometre to 1000 micrometre, preferably from 200 micrometre to 800 micrometre, more preferably from 300 micrometre to 700 micrometre.
[0026] Furthermore, the fibre dosing chamber may comprise more than one actuator for manipulating the discharging portion between the closed position and the open position.
[0027] In an embodiment, the fibre dosing unit further comprises a covering means positioned at least partially inside said drum and directly above said transportation means arranged for covering said transportation means, said covering means comprising an opening through which said portion of said fibres can be discharged onto said transportation means such that a reduced portion of said fibres is discharged on said transportation means. This has the benefit of more controlled discharging of the fibres from the drum to the dosing chamber.
[0028] In an embodiment, said covering means is further arranged to move between back and forth above said transportation means along said longitudinal horizontal axis of said fibre dosing unit for changing a position of said opening. By changing the position of the opening, the amount of the portion of fibres being dropped on the transportation means can be controlled. This allows for more accurate dosing of the fibres.
[0029] In an embodiment, said drum comprises two to twelve collector means, preferably three to eight collector means, more preferably four to six collector means.Having three to eight collector means enables small portions of fibres to be collected from the bulk and discharged onto the transportation means and the time interval to do so can be controlled better with this range of the number of collector means. Hence, it provides more flexibility to controlling of the fibre dosing unit.
[0030] In an embodiment, said at least one collector means has a shape, preferably a longitudinal shape, selected from the group consisting of a scoop, such as a C-shaped scoop, a blade, such as a C-shaped blade, a rib, a baffle, a vane, a fin, an internal spiral or helix. The effect of such shapes is that a portion of fibres can be collected easier from the bulk of fibres.
[0031] In an embodiment, said drum comprises a fibre feeding opening arranged for feeding said fibres to said drum during operation of said drum. A fibre feeder may be coupled with said fibre feeding opening such that fibres can be fed to the drum during operation of the drum in a continuous manner. The fibre feeder may further comprise a funnel for easier filling.
[0032] In an embodiment, the fibre dosing unit further comprises a further sensor means arranged for measuring an overall weight of said fibres in said drum, and wherein said control unit is arranged to provide a notification to provide fibres to said drum, preferably through said fibre feeding opening, once said overall weight of said fibres in said drum drops below a predefined threshold weight value. This enables the fibre dosing unit to keep operating, i.e. , dosing fibres, in a continuous manner such that the system can keep on printing. The further sensor means may be one sensor arranged in a supporting structure, such as a plate, upon which the fibre dosing unit is placed. The further sensor means may also be multiple sensors, each sensor being arranged in a supporting leg of the fibre dosing unit.
[0033] In an embodiment, said drum is oriented at an inclination angle up to 30 degrees relative to a longitudinal horizontal axis of said fibre dosing unit. Such an orientation has the effect that due to gravity during rotation the fibres flow to the lowest point inside the drum. This accommodates for a controlled collection of fibres by the one ormore collector means. The skilled person will understand that with “up to 30 degrees is meant any angle larger than 0 degrees up to and including 30 degrees.
[0034] In an embodiment, said drum has a spheroid shape, such as an ellipsoid shape or ovoid shape, preferably said drum has an ellipsoid shape. Such a shape, specially when the drum is oriented at an inclination angle, has the effect that due to gravity during rotation the fibres flow to the lowest point inside the drum. This accommodates for a controlled collection of fibres by the one or more collector means.
[0035] In an embodiment, said one or more collector means has a height that is from 1 to 30 % of an inner width diameter of said drum, preferably 3 to 20 %, more preferably 5 to 10 %. This provides an optimal balance between the collecting of as many fibres as possible from the bulk of fibres with a single collector means and the physical limitations inside the drum.
[0036] In an embodiment, said drum has a length to inner width diameter ratio of from 0.02 to 50, preferably 0.2 to 25, more preferably 1 to 10, most preferably 2 to 5. Such a ratio allows more efficient agitating of the bulk of fibres and collecting portions of fibres for discharging said portions of fibres onto the transportation means.
[0037] In an embodiment, said speed of rotation of said drum is from 5 to 100 rpm, preferably 10 to 70 rpm, more preferably 15 to 50 rpm, such as 40 rpm. The desired speed of rotation depends on the dimensions of the drum and the dosing settings of the fibre dosing units, e.g., weight of portion of fibres that is dosed during each time interval and the length of each time interval. Hence, the dosing can be adjusted by adjusting the speed of rotation of the drum.
[0038] In an embodiment, said transportation means is a conveyor belt.
[0039] In an embodiment, said speed of transportation of said fibres on said transportation means is from 50 to 500 m / s, preferably 100 to 300 m / s. The desired speed of transportation of the fibres on the transportation means depends on the dimensions of the transportation means and the dosing settings of the fibre dosingunits, e.g., weight of portion of fibres that is dosed during each time interval and the length of each time interval. Hence, the dosing can be adjusted by adjusting the speed of transportation of the fibres on the transportation means to the fibre dosing chamber.
[0040] In an embodiment, said predefined constant time interval is from 1 to 15 s, preferably 4 to 12 s, more preferably 6 to 10 s. Such predefined constant time interval ranges provide more flexibility of dosing fibres with the fibre dosing unit to the print head or to a mixing unit of the print head of the system in a continuous-type of manner.
[0041] In an embodiment, said predefined fibre dosing rate is from 1 to 500 g / min, preferably 5 to 350 g / min, more preferably 10 to 250 g / min. This is beneficial as it provides more flexibility of dosing fibres with the fibre dosing unit to the print head or to a mixing unit of the print head of the system in a continuous-type of manner.
[0042] In an embodiment, said fibre dosing unit is connected to a print head of said system for three-dimensional printing. The fibre dosing unit may be connected directly to the print head or connected indirectly to the print head via a transportation means that is arranged for transporting the fibres to the print head or to a mixing unit of the print head.
[0043] The method according to the second aspect of the present invention may further comprise a feeding step, wherein the drum is fed with fibres via the fibre feeding opening during operation of the drum.BRIEF DESCRIPTION OF THE DRAWINGS
[0044] The present invention is described hereinafter with reference to the accompanying drawings in which embodiments are shown and in which like reference numbers indicate the same or similar elements. The invention is in no manner whatsoever limited to the embodiments disclosed therein.Fig. 1 shows a fibre dosing unit;Fig. 2 shows a cross-sectional view along line A-A of the fibre dosing unit ofFig. 1 ;Fig. 3 shows a side view of part of a fibre dosing unit;Fig. 4A shows a dosing chamber of a fibre dosing unit;Fig. 4B shows a dosing chamber of a fibre dosing unit;Fig. 5 shows a method of introducing fibres with a fibre dosing unit.DETAILED DESCRIPTION OF THE DRAWINGS
[0045] A fibre dosing unit 1 for introducing fibres to a print head of a system for three- dimensional printing of a structure with a fibre-reinforced mixture is shown in Fig. 1. The fibre dosing unit 1 comprises a drum 3 and is arranged for rotating around a rotation axis R with a speed of rotation and is arranged for storing the fibres, wherein the fibres (not shown) are provided in bulk to the drum 3. The drum 3 has a length L and an ellipsoid shape.
[0046] The fibre dosing unit 1 of Fig. 1 further comprises a transportation means 11 , positioned at least partially inside the drum 3 and below an inner top side 9 of the drum 3 for collecting discharged portions of the fibres on the transportation means 11. The transportation means 11 are arranged to transport fibres collected on the transportation means 11 with a speed of transportation into a fibre dosing chamber 13. A covering means 33 is provided partially inside the drum 3 and directly above the transportation means 11. The covering means 33 is arranged for covering the transportation means 11 and comprises an opening 35 through which the portion of fibres can be discharged onto the transportation means 11 such that a reduced portion of the fibres is discharged on the transportation means 11.
[0047] The fibre dosing chamber 13 comprises a receiving portion 15 at a top side 17 of the fibre dosing chamber 13 and the receiving portion 15 is arranged for receiving the fibres from the transportation means 11. The fibre dosing chamber 13 further comprises a discharging portion 19 at a bottom side 21 of the fibre dosing chamber 13 and the discharging portion 19 is arranged for discharging the fibres from the fibre dosing chamber 13. Further, the fibre dosing chamber 13 comprises an actuator 23 arranged for manipulating the discharging portion 19 between a closed position 25 and an open position 27.
[0048] The fibre dosing unit 1 shown in Fig. 1 further comprises a control unit 29 for controlling the actuator 23, the speed of transportation of the fibres on the transportation means 11 , and the speed of rotation of the drum 3. The control unit 29 is further arranged for receiving a value of a weight of the fibres in the fibre dosing chamber 13 from sensor means 31 arranged for measuring the weight of the fibres in the fibre dosing chamber 13.
[0049] The control unit 29 is arranged to control the speed of transportation of the fibres on the transportation means 11 and the speed of rotation of the drum 3 in accordance with a predefined fibre dosing rate, and with a predefined constant time interval of manipulating the discharging portion 19 between the closed position 25 and the open position 27. The predefined fibre dosing rate is defined by the weight of the fibres in the fibre dosing chamber 13 exceeding a predefined threshold weight value.
[0050] The drum 3 further comprises a feeding opening 37 arranged for feeding fibres to the drum 3 during operation of the drum 3 and a funnel 41 arranged on top of the feeding opening 37. The fibre dosing unit 1 comprises a further sensor means 39 arranged for measuring an overall weight of the fibres in the drum 3. The further sensor means 39 contains four sensors, wherein each sensor is comprised each leg of the fibre dosing unit 1 . The control unit 29 is arranged to provide a notification to add fibres to the drum 3 once the overall weight of the fibres in the drum 3 drops below a predefined threshold weight value.
[0051] Fig. 2 shows a cross-sectional view along line A-A of the drum 3 of the fibre dosing unit 1 of Fig. 1. The drum 3, having an inner width diameter D, comprises four more collector means 5 attached to an inner wall 7 of the drum 3 and the collector means 5 are arranged for transporting a portion of the fibres upwards for discharging said portion of fibres at or near an inner top side 9 of the drum 3. Each of the collector means 5 has a height H.
[0052] A side view of the drum 3 and part of the transportation means 11 of the fibre dosing unit 1 is shown in Fig. 3. As shown, the drum is oriented at an inclination angle a relative to a longitudinal horizontal axis X of the fibre dosing unit 1.
[0053] A close-up view of the fibre dosing chamber 13 is shown in Fig. 4A and Fig. 4B. In Fig. 4A, the discharging portion 19 is positioned in the closed position 25 and in Fig. 4B, the discharging portion 19 is positioned in the open position 27.
[0054] Fig. 5 shows a flow chart of a method 101 of introducing fibres with a fibre dosing unit 1 to a print head of a system for three-dimensional printing of a structure with a fibre-reinforced mixture. The method 101 comprises the steps of providing 103 fibres in bulk to the drum 3; transporting 105, with the one or more collector means 5 attached to the inner side 7 of the drum 3, the portion of fibres upwards for discharging the portion of fibres at or near the inner top side 9 of the drum 3; collecting 107, with the transportation means 11 , discharged portions of the fibres on the transportation means 11 ; transporting 109, with the transportation means 11 , fibres collected on the transportation means 11 to the fibre dosing chamber 13; discharging 111 , by manipulating with the actuator 23 the discharging portion 19 from the closed position 25 to the open position 27, fibres from the fibre dosing chamber 13; measuring 113, wit the sensor means 29, the weight of the fibres in the fibre dosing chamber 13; and controlling 115, with the control unit 29, the speed of transportation of the fibres on the transportation means 11 and the speed of rotation of the drum 3.
[0055] Modifications and additions to the embodiments disclosed above are obvious to those skilled in the art and covered by the scope of the appended claims. Embodiments and examples of the first aspect of the present invention are also applicable to the second and third aspects of the present invention.
[0056] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof. One or more of the objects of the invention are achieved by the appended claims.
Claims
1. A fibre dosing unit (1) for introducing fibres to a print head of a system for threedimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, said fibre dosing unit (1) having a longitudinal horizontal axis (X) and comprising:- a drum (3) arranged for rotating around a rotation axis (R) and arranged for storing said fibres, provided in bulk to said drum (3), said drum (3) comprising:- one or more collector means (5) attached to an inner wall (7) of said drum (3) and arranged for transporting a portion of said fibres upwards for discharging said portion of said fibres at or near an inner top side (9) of said drum (3);- a transportation means (11), positioned at least partially inside said drum (3) and below said inner top side (9) for collecting discharged portions of said fibres on said transportation means (11); wherein said transportation means (11) are arranged to transport fibres collected on said transportation means (11) into:- a fibre dosing chamber (13) comprising:- a receiving portion (15) at a top side (17) of said fibre dosing chamber (13) and arranged for receiving said fibres from said transportation means (11),- a discharging portion (19) at a bottom side (21) of said fibre dosing chamber (13) and arranged for discharging said fibres from said fibre dosing chamber (13),- an actuator (23) arranged for manipulating said discharging portion (19) between a closed position (25) and an open position (27);- a control unit (29) for controlling said actuator (23), a speed of transportation of said fibres on said transportation means (11), and a speed of rotation of said drum (3), wherein said control unit (29) is further arranged for receiving a value of a weight of said fibres in said fibre dosing chamber (13), received from:- sensor means (31) arranged for measuring said weight of said fibres in said fibre dosing chamber (13),characterized in that said control unit (29) is arranged to control said speed of transportation of said fibres on said transportation means (11) and said speed of rotation of said drum (3) in accordance with a predefined fibre dosing rate, defined by said weight of said fibres in said fibre dosing chamber (13) exceeding a predefined15threshold weight value, and a predefined constant time interval of manipulating said discharging portion (19) between said closed position (25) and said open position (27).
2. Fibre dosing unit (1) according to claim 1, further comprises a covering means (33) positioned at least partially inside said drum (3) and directly above said transportation means (11) arranged for covering said transportation means (11), said covering means (33) comprising an opening (35) through which said portion of said fibres can be discharged onto said transportation means (11) such that a reduced portion of said fibres is discharged on said transportation means (11).
3. Fibre dosing unit (1) according to claim 1 or 2, wherein said covering means (33) is further arranged to move between back and forth above said transportation means (11) along said longitudinal horizontal axis (X) of said fibre dosing unit (1) for changing a position of said opening (35).
4. Fibre dosing unit (1) according to any of the preceding claims, wherein said drum (3) comprises two to twelve collector means (5), preferably three to eight collector means (5), more preferably four to six collector means (5).
5. Fibre dosing unit (1) according to any of the preceding claims, wherein said at least one collector means (5) has a shape, preferably a longitudinal shape, selected from the group consisting of a scoop, such as a C-shaped scoop, a blade, such as a C-shaped blade, a rib, a baffle, a vane, a fin, an internal spiral or helix.
6. Fibre dosing unit (1) according to any of the preceding claims, wherein said drum (3) comprises a fibre feeding opening (37) arranged for feeding said fibres to said drum (3) during operation of said drum (3).
7. Fibre dosing unit (1) according to any of the preceding claims, further comprising a further sensor means (39) arranged for measuring an overall weight of said fibres in said drum (3), and wherein said control unit (29) is arranged to provide a notification to provide fibres to said drum (3), preferably through said fibre feeding16opening (37), once said overall weight of said fibres in said drum (3) drops below a predefined threshold weight value.
8. Fibre dosing unit (1) according to any of the preceding claims, wherein saiddrum (3) is oriented at an inclination angle (a) up to 30 degrees relative to said longitudinal horizontal axis (X) of said fibre dosing unit (1).
9. Fibre dosing unit (1) according to any of the preceding claims, wherein said drum (3) has a spheroid shape, such as an ellipsoid shape or ovoid shape, preferably said drum (3) has an ellipsoid shape.
10. Fibre dosing unit (1) according to any of the preceding claims, wherein said one or more collector means (5) has a height (H) that is from 1 to 30 % of an inner width diameter (D) of said drum (3), preferably 3 to 20 %, more preferably 5 to 10 %.
11. Fibre dosing unit (1) according to any of the preceding claims, wherein said drum (3) has a length to inner width diameter (L:D) ratio of from 0.02 to 50, preferably 0.2 to 25, more preferably 1 to 10, most preferably 2 to 5.
12. Fibre dosing unit (1) according to any of the preceding claims, wherein said speed of rotation of said drum (3) is from 5 to 100 rpm, preferably 10 to 70 rpm, more preferably 15 to 50 rpm.
13. Fibre dosing unit (1) according to any of the preceding claims, wherein said transportation means (11) is a conveyor belt.
14. Fibre dosing unit (1) according to any of the preceding claims, wherein said speed of transportation of said fibres on said transportation means (11) is from 50 to 500 m / s, preferably 100 to 300 m / s.
15. Fibre dosing unit (1) according to any of the preceding claims, wherein said predefined constant time interval is from 1 to 15 s, preferably 4 to 12 s, more preferably 6 to 10 s.1716. Fibre dosing unit (1) according to any of the preceding claims, wherein said predefined fibre dosing rate is from 1 to 500 g / min, preferably 5 to 350 g / min, more preferably 10 to 250 g / min.
17. A system for three-dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, comprising a fibre dosing unit (1) according to any of the claims 1 to 16.
18. A method (101) of introducing fibres with a fibre dosing unit (1) according to any of the claims 1 to 16 to a print head of a system for three-dimensional printing of a structure, such as a concrete structure, with a fibre-reinforced mixture, said method (101) comprising the steps of:- providing (103) said fibres in bulk to said drum (3);- transporting (105), with said one or more collector means (5) attached to saidinner wall (7) of said drum (3), said portion of said fibres upwards for discharging said portion of said fibres at or near said inner top side (9) of said drum (3);- collecting (107), with said transportation means (11), discharged portions of said fibres on said transportation means (11);- transporting (109), with said transportation means (11), fibres collected on said transportation means (11) to said fibre dosing chamber (13);- discharging (111), by manipulating with said actuator (23) said discharging portion from said closed position (25) to said open position (27), fibres from said fibre dosing chamber (13);- measuring (113), with said sensor means (31), said weight of said fibres in said fibre dosing chamber (13);- controlling (115), with said control unit (29), said speed of transportation of said fibres on said transportation means (11) and said speed of rotation of said drum (3).
19. A computer program product, comprising a data storage device storing computer program code arranged for performing a method (101) according to claim 18, when said computer program code are loaded onto a memory of an electronic processing unit when executed by said electronic processing unit.