Abstract
A print head for printing three-dimensional structures made of concrete and a method used to deposit layers of concrete material one on top of the other. The print head is configured to be moved in space and to deposit individual layers of a concrete material, which forms the structure to be produced, one on top of the other. The print head includes a feeder configured to provide the concrete material, a conveying device configured to receive the concrete material from the feeder and to convey it, a shaping section configured to be filled with the pressurized concrete material and to define lateral dimensions of the layer to be deposited, an exit section pointing in a direction opposite to a feed direction of the print head, and an exiting prevention section configured to prevent the concrete material from exiting in the feed direction of the print head.
Claims
1. A print head for printing three-dimensional structures made of concrete, where said print head is configured to be moved in space and to deposit individual layers of a concrete material one on top of the other which forms the structure to be produced, said print head comprising: a feeder which is configured to provide said concrete material, a conveying device which is configured to receive said concrete material from said feeder and convey it, a shaping section which is configured to be filled by the pressurized concrete material and to define at least the lateral dimensions of said layer to be deposited, an exit section pointing in a direction opposite to a feed direction of said print head, an exiting prevention section which is configured to prevent said concrete material from exiting in the direction of said feed direction of said print head, wherein said conveying device is an auger device.
2. The print head according to claim 1, where said print head comprises a pressure compensation section, preferably within said shaping section.
3. The print head according to claim 1, where said print head further comprises an energy supply device which is configured to supply energy to said concrete material within said shaping section.
4. The print head according to claim 1, where said shaping section comprises a controllable profiling device which is configured to be able to vary the layer thickness of the layer to be deposited.
5. The print head according to claim 4, where said profiling device is configured to form at least one section along the width direction of said layer made of concrete material to be concave with regard to the layer thickness.
6. The print head according to claim 4, where said profiling device is configured to form at least in sections at least two strands spaced apart and running parallel to one another.
7. The print head according to claim 4, where said profiling device forms the pressure compensation device.
8. The print head according to claim 7, where said profiling device comprises at least one elastic element and at least one flap, and said flap is attached to said print head by way of said elastic element.
9. The print head according to claim 1, where said print head further comprises a binding material processing device which is configured to deposit at least one layer of a binding material between adjacent layers of the concrete material.
10. The print head according to claim 9, where said binding material processing device comprises an exit section which opens substantially downwardly.
11. The print head according to claim 1, where said print head additionally comprises a magazine for storing reinforcement elements or connection elements, and a reinforcement insert device which is configured to insert reinforcement elements or connection elements horizontally or vertically into said layers of concrete material.
12. The print head according to claim 1, where said print head further comprises a trowel smoothing device which is configured to rub off the transitions of said already deposited layers and to thereby smooth them, where said trowel smoothing device is preferably configured to guide said print head.
13. A method in which a print head according to claim 1 is used to deposit layers of concrete material one on top of the other, where a concrete with a dry mixing ratio, preferably with a water/cement ratio (w/c) between 0.23 and 0.35 is used as concrete material.
Description
[0037] Further details and preferred embodiments shall be illustrated with the following figures, where
[0038] FIG. 1 shows the print head according to the invention
[0039] FIG. 2A shows an oblique view of the print head from FIG. 1
[0040] FIG. 2B shows an oblique view of the print head from FIG. 2A
[0041] FIG. 3 shows a further embodiment of the print head according to the invention in a sectional view
[0042] FIG. 4 shows a cross-sectional view through the processed concrete material
[0043] FIG. 5 shows the print head according to the invention with a viewing direction onto the exit section
[0044] FIG. 6 shows a cross-sectional view through the processed concrete material
[0045] FIG. 7 shows a double wall produced with the aid of the print head according to the invention in a top view.
[0046] FIG. 1 schematically shows a print head 1 according to the invention in use with which several layers of concrete material 20a and several layers of a binding material 20b have already been deposited in order to print a three-dimensional structure made of concrete. The print head moves at a certain feed rate along a direction of arrow A which defines the longitudinal extension of the individual layers. The width direction of the layer runs transverse to the longitudinal direction of the layers or transverse to the feed direction into the plane of the drawing. The layer thickness direction is defined by the stacking direction of the individual layers. The drive for providing the advance of print head 1 is not shown for reasons of clarity. In stationary systems, for example, the print head can be driven via a frame within which the structure to be printed is to be created. Print head 1 would slide or roll along guide rails and also be movable in height in order to be able to print individual layers 20a, 20b. For mobile applications, such as construction sites, the print head can also be moved by way of an arm that can be moved in space. In the situation shown in FIG. 1, print head 1 deposits a further layer 20a of concrete material.
[0047] In the three-dimensional view in FIG. 2A of print head 1 and in the sectional view in FIG. 2B, print head 1 according to the invention is again shown in simplified form. Print head 1 comprises a feeder 2. The purpose of feeder 2 is to supply print head 1 movable in space with concrete material.
[0048] The material can be fed into feeder 2, for example, by way of a concrete pump, while print head moves in space. Print head 1 including the material has a small mass, which allows print head 1 to be moved precisely in space and facilitates the support of print head 1. On the other hand, print head 1 can also be filled with material prior to the movement process. A concrete with a dry mix ratio having a water/cement ratio between 0.23 and 0.35 is preferably used as concrete material. The water/cement ratio (w/c) indicates a mass ratio between the mass of water present in 1 m.sup.3 of concrete compared to cement.
[0049] Furthermore, print head 1 comprises conveying device 3 which is presently configured as an auger device. As shown in FIG. 2A, conveying device 3 is preferably configured in the form of two augers. The alternating engagement of the auger threads with the material results in good mixing and a homogeneous material. Conveying device 3, however, can also be formed by only one auger or by a pump. Conveying device 3 is supplied with material from feeder 2 and conveys it into a shaping section 4 in a direction opposite to the feed direction based on the principle of forced conveyance. The auger preferably has an enlarging section 3a in which the auger diameter increases and the gap width between auger 3 and housing wall 3b decreases. The concrete material is there compressed and the shear rate increases due to the smaller gap width, which causes a pressure build-up in the material. The concrete material is therefore conveyed subject to pressure into shaping section 4. Due to the fact that the material fills shaping section 4 subject to pressure, the material can completely fill the cross section of shaping section 4, in particular over the entire width of shaping section 4. The pressure in the material causes the concrete to be dimensionally stable and to begin to set. At least the lateral dimensions of the layer to be deposited can thereby be defined by shaping section 4. The material, which is defined in cross section at least with regard to the lateral dimensions, exits into the open from an exit section 5 that points in a direction opposite to feed direction A without changing the lateral dimensions since the material has good dimensional stability due to the low w/c ratio. Exiting prevention section 6 is additionally provided and prevents the concrete material, which can also flow in the feed direction due to the pressure built up, from exiting from print head 1 in feed direction A. A space is created that is closed in the feed direction on five sides by housing wall 3b above, below and laterally on both sides as well as exiting prevention section, and the layer can be deposited along a defined direction opposite to feed direction A and a build-up of concrete material in front of the print head can be prevented. A stable layer with a good surface quality can thus be deposited. Furthermore, as shown in FIGS. 2A and 2B, print head 1 preferably comprises a binding material processing device 8. At least one layer 20b of binding material can be applied with binding material processing device 8 between adjacent layers 20a of the concrete material, as shown in FIG. 1. The binding material is preferably concrete having a higher water/cement ratio, jointing mortar, or even industrial adhesive. The dry concrete material which promotes rapid setting can under certain circumstances cause poor bonding with next layer 20a. Layer 20b of binding material bonds individual layers 20a of concrete material to one another and thereby eliminates the joint as a weak point. As shown in FIG. 2B, binding material processing device 8 preferably comprises an exit section 8a which opens substantially downwardly. This allows the binding material to be applied to the layer of concrete disposed therebeneath by the action of gravity, which enables simple processing. Exit section 8a is preferably arranged in feed direction A upstream of exit section 5 for the concrete material. The binding material is then already applied to layer 20a of the concrete material disposed therebeneath and can be distributed over a large area by the weight of layer 20a made of concrete material to be deposited. Excess binding material would there be squeezed out to the side.
[0050] As shown in FIG. 1, the print head can furthermore comprise an energy supply device 14. In FIG. 1, this energy supply device 14 is configured in the form of heating strips along shaping section 4. Alternatively, vibrating plates can also be provided which vibrate the concrete either in shaping section 4 or already downstream of exit section 5 at the edges at a certain frequency, for example, 120 Hz. The concrete material can also be irradiated with microwaves. With all of these methods, the concrete material is supplied with energy which accelerates the setting of the material, so that the material exits from the exit section in a substantially dimensionally stable manner or continues to set quickly thereafter. This further increases the stability and surface quality of the structure.
[0051] FIG. 1 further shows disk-shaped trowels 15, which form the trowel smoothing device according to the present invention and are attached to the print head on both sides of print head 1. This trowel smoothing device 15 can smoothly process the layers that have already been deposited by rubbing off material, where the surface quality and the dimensional accuracy of the lateral dimensions of the structure is improved. In particular, excess binding material can thus be removed and collected, for example, in a collection container 16. Furthermore, trowel smoothing device 15 can guide the print head, since the former is suitable to prevent a motion transverse to the feed direction in a horizontal direction by preventing the disk-shaped trowels from moving in this direction by the layers that have already been deposited.
[0052] A further embodiment is shown in FIG. 3. Print head 1 is similar to print head 1 of the first embodiment. Print head 101, however, comprises a modified shaping section 104. It consists of a tapering section 104a running towards layer 20a disposed therebeneath and a straight section 104b running in a direction opposite to feed direction A. Since tapering section 104a is provided, the pressure upstream of shaping section 104 can be increased further by damming up the material. This pressure is then relieved in tapered section 104a while the concrete material flows through the incline of tapered section 104a to the layer disposed therebeneath. The height offset between the axis of augers 3 can then be eliminated gently, and there is no sudden drop in the concrete material at exit section 5. The material sets subject to the remaining pressure in section 104b. Section 104b is no longer defined only by housing wall 3b, but by lower layer 20a made of concrete material. The concrete material should still be flowable at the transition between inclined tapered section 104a and the straight section in order to prevent it from getting stuck.
[0053] Furthermore, print head 101 comprises a profiling device 7 which is located within shaping section 104. Profiling device 7 is formed by an elastic element 7a and a flap 7b. Profiling device 7 creates the possibility of depositing layers of different thicknesses with one and the same print head. Flap 7b can be rotated to various positions, for example, by use of a motor. Accordingly, it can protrude into the cross section of shaping section 104 at different depths and thereby configure the layer thickness, i.e., the height of the layer, differently from layer to layer. Flap 7b, however, can also be adjusted while a layer is being deposited and the layer thickness can then also be varied within a layer in the longitudinal direction of the layer. Furthermore, flap 7b does not have to be formed over the entire width of the shaping section, but can also be provided only in a section in the width direction of shaping section 104, which is why the layer thickness varies in the width direction of the layer. Flap 7b then creates at least one section that is concave with respect to the layer thickness along the width direction of layer 20a of concrete material. This allows material from the layer disposed thereabove to simply flow into this concave section. This results in a positive fit between adjacent layers, which ensures good stability of the printed structure. This is shown by way of example in FIG. 4, which shows a cross section through the printed structure. A concave section 30 can be formed into which material of layer 20a disposed thereabove flows and sets there. Furthermore, profiling device 7 is configured as the pressure compensation device in print head 101. By connecting flap 7b to print head 101 by way of elastic element 7a, flap 7b can be adjusted subject to pressure fluctuations. The pressure fluctuation is compensated for in this manner and the layer thickness is varied locally if necessary. These changes in layer thickness can be compensated for with the layers disposed thereabove.
[0054] In FIG. 4, a concave section 30 is also provided on the right-hand side. However, layers 20a are provided with a cavity 40. This cavity 40 can be introduced into the layer, for example, by way of a mandrel which is fastened by webs to housing wall 3b of the shaping section. This makes the structure particularly light because material is saved.
[0055] FIG. 5 finally schematically shows a print head with a viewing direction onto exit section 5 of the print head. As shown in FIG. 5, the print head comprises several flaps 7b across the width direction of the shaping section which protrude from the upper side into the shaping section. These flaps 7b are adjustable and can be actuated individually, and different contours with alternating concave and convex sections can then be created on the upper side of the layer. Bonding of the individual layers can then be further improved. It is also possible to make individual flaps 7b assume the completely closed position. The closed position of a flap 7b is the one in which flap 7b rests on the lower layer. The cross section in the shaping section can thereby be closed in part in the width direction. If the outer ones of the plurality of flaps 7b are made to assume a closed position in the width direction, then the width of the layer to be deposited can be varied. If, on the other hand, an internal flap 7b is made to assume a closed position, then the layer to be deposited can be divided at least in sections into at least two strands extending in parallel which exit from exit section 5 in a dimensionally stable manner. At least two strands spaced apart transverse to the feed direction of the print head exit from the exit section 5. For example, a double wall can thus be produced.
[0056] FIG. 6 shows a detail of a layer 20a made of concrete material, where a concave section 31 was provided in the longitudinal direction of the layer. This section can be obtained, for example, by collectively lowering the flaps of the print head in FIG. 5 to a position closed in part. A reinforcement element 9 can be inserted into such a concave section 31 and is concreted in with the subsequent layer. Reinforcement element 9 can also protrude laterally from layer 20a and protrude into an oppositely disposed concave section 31 of same layer 20a. The stability between individual layer sections can thus be improved.
[0057] This is particularly advantageous when producing a double wall, where it is possible for concave sections 31 to be provided in the parallel strands at the same position or also at alternating positions in the feed direction of the print head. A double wall is shown in FIG. 7 by way of example in a top view. The double wall is formed in that each deposited layer is formed by two strands 21 and 22 extending in parallel and spaced apart. Furthermore, the strands extending in parallel can be stabilized by way of reinforcement elements or connection elements 9 in a horizontal direction transverse to the feed direction. These reinforcement elements can be removed by a reinforcement insertion device from a magazine, which the print head comprises, and inserted into the layers of concrete material. FIG. 7 shows a lattice-like connection element 9 which connects two strands 21 and 22 to one another in a horizontal direction. In this case, for example, concave sections can be provided at alternating positions with respect to strands 21 and 22 in the feed direction of the print head and facilitate the insertion of the connection element. When the space between the wall parts formed by strands 21 and 22 is subsequently filled with in-situ concrete, higher concreting speeds can be employed.
