Patent Application
20210394441
The object of the invention are the device and method for the creating of supports, formworks, and structures made of foamed plastics, and the method for the creating of constructions, which can be used especially for the incremental creation of concrete structures, as well as the device and method for the creating of constructions, especially those made of concrete.
A system for additive printing, which allows to create three-dimensional structures by extrusion, including with the possible use of foaming substances, is known from European patent EP3081364 B1. However, this document does not in any way consider the use of this technology when creating concrete structures.
US patent application US2017106592 A1 describes the challenges of creating concrete buildings using 3D printing technology. It is proposed to pour concrete mix over previously formed moulds that are created by the spraying of foamed materials. However, the disadvantage of such a solution is the necessity (indicated in the document) to process the surface of the created moulds later, in order to align them to an acceptable level—which makes it necessary to use an additional tool. A similar solution is the object of the patent application US2016001461 A1, which additionally considers various methods for easy removal of the created moulds/supports, including by dissolving the material of a support (e.g. wax) at an increased temperature so as to recover at least some of the material. However, neither document considers the various aspects of foaming the material that is intended for the mould/support, and neither document allows complete freedom and ease of use of various materials intended for supports/moulds.
The purpose of the invention is to provide a device and method for the creating of building supports that would be easily usable when creating constructions using 3D printing techniques.
The object of the invention is the device for the creating of supports, formworks, or structures made of foamed plastic, designed to be placed on a controlled manipulator, having means for the supplying of plastic, especially plastic in the form of pellets, such as a storage container, or means for pneumatic transport, a screw extruder sleeve, especially a heated one, an extruder screw, a blowing agent feeding assembly, and preferably an outlet nozzle located at the end of the extruder sleeve, characterized in that the blowing agent feeding assembly includes a compressor, possibly with a buffer tank, a pump, or means adapted to the supplying of the blowing agent from outside the device, where this assembly is adapted to the supplying of the blowing agent as compressed gas, liquid, or supercritical liquid, where the device is configured so that, under normal use, in the extruder sleeve the blowing agent is mixed with the plastic, and at the extruder outlet the blowing agent expands and the physical foaming of the plastic occurs.
Preferably, the device additionally has an outlet nozzle placed at the end of the extruder sleeve and, additionally, has a return channel whose one end connects with the extruder sleeve at a place before the outlet nozzle, as well as an extruder nozzle closing element.
Preferably, the device additionally has a dye storage container or means for the supplying of dye from outside the device that are connected to the extruder sleeve.
Preferably, the device additionally has a concrete mortar depositing nozzle.
Preferably, the device additionally has a solvent spraying assembly.
Preferably, the device additionally has an air supplying assembly, which preferably has means for the heating and/or cooling of the air stream.
Preferably, the device additionally has a separation layer depositing assembly, especially in the form of a powder storage container and a vibratory conveyor, or a pneumatic atomizer.
Preferably, the device has an outlet nozzle located at the end of the extruder sleeve and, additionally, means for the levelling of the surface of the foamed plastic being deposited, especially in the form of a cutting or heating tool, where these means are preferably located near the end of the outlet nozzle.
The object of the invention is also the device for the creating of concrete constructions, especially in the incremental printing technique, characterized in that it has a device for the creating of supports.
The object of the invention is also the method for the creating of supports, formworks, or structures made of foamed plastic, which uses a digitally controlled device that has a printhead placed on a manipulator able to move the head in space, where the printhead has a screw extruder with a sleeve, where the extruder is supplied with a plastic, preferably in the form of pellets, characterized in that the extruder sleeve is supplied with a blowing agent in the form of compressed gas, liquid, or supercritical liquid, chemically inert to the used plastic, this plastic is mixed with the blowing agent in the extruder sleeve, and at the extruder outlet the blowing agent expands and the physical foaming of the plastic occurs, which foamed plastic is used to create an element made of foamed plastic such as a support, formwork, or structure.
Preferably, nitrogen or carbon dioxide are used as the blowing agent.
Preferably, the blowing agent is supplied to the extruder sleeve at a pressure ranging from 1 to 250 bar, preferably from 3 to 200 bar, and the most preferably from 5 to 150 bar.
Preferably, after the foamed plastic element has been created, its surface is levelled with a movable cutting tool.
Preferably, after the foamed plastic element has been created, its surface is levelled by locally melting the surface of the foamed plastic, especially with the use of a heated tool, intense radiation, or blowing with hot air.
Preferably, after the foamed plastic element has been created and its surface optionally levelled, the surface of the foamed plastic element is covered with a separation layer.
Preferably, the separation layer is made of a thermoplastic material, especially wax, or a water-soluble substance, especially polyvinyl alcohol.
Preferably, the separation layer is made of dust or powder, especially mineral.
Preferably, the separation layer is made of a substance characterized by low adhesion to concrete, especially paint or lacquer.
Preferably, after the foamed plastic element has been created, its surface is sprayed with a small amount of solvent.
Preferably, the properties (especially mechanical or thermal properties) of the foamed plastic element are adjusted by changing the pressure of the supplied blowing agent.
Preferably, while creating the foamed plastic element, the purpose of the individual parts of the foamed plastic element is differentiated by colouring these parts differently.
The object of the invention is also the method for the erecting of concrete constructions, especially in the incremental printing technology, which method is characterized in that the supports or formworks are made of foamed plastics using the method according to the invention.
The invention will now be presented in more detail using a preferable embodiment, with reference to the enclosed drawings, where:
The device for the creating of supports according to the invention uses the technique of extrusion of materials that become physically foamed.
The extruder sleeve (2) and the extruder screw (3) are made of a material that must be chemically inert to the substances that may possibly be introduced into it, as well as adequately resistant to any mechanical loads resulting from the need to achieve high pressures (in order to be able to physically foam the plastic) and adequately resistant to any high temperatures resulting from the need to plasticize the plastics. The sleeve (2) and the screw (3) can be made of the same material or of different materials, according to the expected operating conditions. Preferably, they are made of steel, especially stainless steel.
The extruder additionally has means for heating the material being moved through the extruder sleeve (2), so that the material being foamed inside the extruder can be plasticized. Various types of heaters can be used, in particular electric heaters built into the walls of the extruder sleeve (2), built into the extruder screw (3), or coming into contact with the extruder sleeve (2) from its outside. The heaters can be, e.g., resistance heaters, or they can be made of Peltier cells or any other elements that are able to generate heat in a controlled manner.
The means for the supplying of plastic to be used by the device according to the invention reach the upper part of the extruder sleeve (2), where this plastic is preferably supplied in the form of pellets (1). The pellets (1) can be supplied to the extruder sleeve in various ways, according to the desired configuration of the device. In one of the embodiments, the pellets (1) may be held in a storage container from which they would fall into the extruder sleeve (2). Optionally, the falling of the pellets could be controlled by applying a vibratory conveyor. In another embodiment, the pellets could be pressed into the extruder sleeve (2) by means of a feeding screw. In yet another embodiment, the pellets (1)—after leaving the storage container but before entering the extruder sleeve (2)—can be pre-plasticized (liquefied) e.g. by heating. With this solution, it is then possible to force the plasticized material into the extruder sleeve (2) by means of a pump. In another embodiment, the pellets (1) can be held in a storage container distanced from the extruder, and be supplied to the extruder sleeve (2) with the use of means for pneumatic transport. In yet another example, the material intended to be used by the extruder can be supplied to the extruder sleeve (2) via hoses, in liquid form.
Preferably, the material supplied to the extruder is plastic, especially thermoplastic, especially in the form of pellets (1), where said plastic can preferably be a material from the group that includes polystyrene, polylactide, arboform, PET, and polypropylene.
From the point of view of the invention, the material supplied to the extruder may come from recycling (e.g. from PET bottles)—in one of the embodiments, it is possible to replace the storage container for the pellets (1) with a shredding device, thanks to which both popular waste (e.g. bottles) and parts of foamed plastic supports/formworks/structures previously created by the device according to the invention could be recycled.
Preferably, the means for the supplying of plastic also include a block/valve/closure, thanks to which it is possible at any time to start or block any further supply of the plastic to the extruder sleeve (2).
Another important element of the device according to the invention is the blowing agent feeding assembly (4), which feeds especially compressed gas or supercritical liquid. This assembly (4) can include (according to the needs): a compressor, a compressor with a buffer tank (to stabilize the pressure), a pressure gas/supercritical liquid tank, a pump, a pump with a buffer tank. In some embodiments, the blowing agent feeding assembly (4) may include within the device only the hoses/channels through which the blowing agent is to be supplied to the extruder sleeve (2), and the compressor/pump/pressure tank may be located away from the extruder (e.g. when the extruder is located at the end of a robot's arm, the compressor/pump/tank may be located at the base of this robot's arm). It is obvious that when selecting the specific elements to create the blowing agent feeding assembly (4), it is necessary to ensure that these elements are sufficiently resistant, especially to pressure—in some applications, it may be preferable to supply the agent at a pressure of even approx. 250 bar.
Preferably, the blowing agent feeding assembly has a valve/check valve/block so as to prevent the plastic from passing from the extruder sleeve (2) to the blowing agent feeding assembly (4) at a time when this would be undesirable (e.g. when the pump/compressor is stopped, or when the pressure hoses lose their tightness).
Preferably, the blowing agent is selected so that it is chemically inert to the plastic being used—the blowing agent may be a gas, a liquid (e.g. fluoro-hydrocarbons, compressed freon), or a supercritical liquid. In many applications, the blowing agent may be carbon dioxide, nitrogen, or even atmospheric air.
Due to the need to achieve/maintain high pressure in the extruder sleeve, it is possible to use an extruder screw (3) with a core diameter that increases lengthwise (towards the extruder outlet), or to make the pitch of the extruder screw (3) denser towards the extruder outlet.
The extruder is typically ended with an outlet nozzle, which is shaped in such a way that expansion of the blowing agent dissolved in/mixed with the plastic occurs in said nozzle, thanks to which the plastic becomes physically foamed and leaves the outlet nozzle in foamed form.
Preferably, the device according to the invention is placed on a controlled manipulator, e.g., on a system of guides or on a robotic arm. An optional element of the device can be a concrete mortar depositing nozzle (7). Such a nozzle (7) can be supplied with concrete mortar through a hose/channel feeding the mortar, e.g., from a concrete mixer (either standalone or mounted on a truck), but it can also—especially if erecting large constructions and if the device is large-sized—have a reservoir of concrete mortar within the device according to the invention (both near the concrete mortar depositing nozzle (7) and near the base of the system of guides/the base of the robot). The advantage of using a single device that could first create supports/formworks/structures made of foamed plastic, and then pour concrete mortar over them, is that it eliminates the risk of a collision between two independent devices, since only one device needs to be delivered to the building site.
In one of the preferable embodiments presented in
Preferably, the motor/servomotor (102) can have adjustable rotational speed, making it possible to adjust the operating speed of the device (the output of the processed plastic).
In order to ensure proper mixing of the plastic with the blowing agent, a part of the extruder screw may have a mixing section, cooperating with the mixing chamber, being a part of the sleeve (103) and located before the extruder nozzle (106). In another preferable embodiment, the mixing chamber may be passive (without a mixing element connected to the screw (104)), e.g. it may be a labyrinth chamber.
The heater (105), located in the sleeve, can preferably be a resistance coil, whose heating power is directly dependent on the parameters of the supply current. The heater (105) can be a single continuous heater, or it can consist of several heaters placed next to each other along the sleeve (103) power-supplied separately or connected in series—such a configuration can be preferable in a situation where it would be advisable to, e.g., heat the plastic incrementally (e.g. first only to plasticize the plastic, and then—already within the sleeve where the blowing agent has been supplied—more intensely in order to achieve the condition of maximum solubility of the blowing agent in the plastic).
Preferably, the extruder sleeve (103), the return channel (107), and the outlet nozzle (106) can be equipped with means for measuring the temperature, e.g. thermocouples. Such means for measuring the temperature are preferably located at multiple places so as to collect information about the condition of the plastic or blowing agent—this is particularly useful in the area of the outlet from the extruder sleeve (103) (or the outlet nozzle 106—if present), because during the expansion of the blowing agent (and possibly during the boiling of the blowing agent when it is a liquid), the blowing agent absorbs significant amounts of heat which, in turn, may cause excessive cooling of the plastic being foamed and its premature hardening. This can be compensated for by the heater (105) or by additional heating means located in the area of the outlet from the extruder sleeve (103) or the outlet nozzle (106). Preferably, the heater (105) or other additional heating means may be combined with the means for measuring the temperature so that the heater (105) or the additional heating means can operate in a feedback loop, e.g. using PID regulators.
The return channel (107) is a modification that ensures more flexible operation of the device according to the invention. For example, if the device has created a support/formwork/structure and then the device is being moved to another location, it is not desirable for the outlet nozzle (106) to discharge foamed plastic (unnecessary loss of material and possible ‘soiling’ of the construction being created). In such a situation, by activating the solenoid valve/servovalve (108), the flow through the extruder nozzle (106) may be closed, and the flow through the return channel (107) may be opened. It is obvious that—simultaneously with the opening of the flow through the return channel (107)—it is necessary to activate the servovalve/solenoid valve (109), which allows the plastic from the return channel (107) to be reintroduced into the extruder sleeve (103). Also obvious is the fact that in order to prevent damage to the extruder, when the discharge through the outlet nozzle (106) is blocked, it is necessary to suspend the supply of both pellets and blowing agent to the extruder sleeve (103) until the servovalve/solenoid valve (108) is activated again and the flow through the extruder nozzle (106) is allowed.
The return channel (107) preferably has the heater (110) which helps to prevent the plastic from setting in the return channel (107). Preferably, this return channel heater (110) is located along and on the outside of the return channel (107). Preferably, the heater (110) has means for maintaining a constant temperature, e.g. a thermostat.
Optionally, the return channel (107) can also have a driven screw which—after restarting the device and allowing flow through the outlet nozzle (106)—would be supposed to push the plastic out of the return channel (107) and back into the extruder sleeve (103).
Preferably, near the outlet nozzle (106), there are means for the levelling of the surface of the foamed plastic being deposited, especially a cutting or heating tool (111). This tool may be put into motion, e.g. rotational motion around the extruder outlet nozzle (106), e.g. using the smoothing tool drive (112). The means for the levelling of the surface of the foamed plastic being deposited may take the form of e.g. a cutter or a blunt element that cuts/scrapes off the surface of the plastic being deposited. In another preferable embodiment, the means for the levelling of the surface can take the form of a heating element which, by coming into contact with the plastic being deposited, would melt its surface thus smoothing it out. In yet another embodiment, the means for the levelling of the surface may include a radiation generator, e.g. a laser or a lamp. In such a case, the surface would be melted by intensive radiation—in such a configuration it is also possible to use optical means for measuring the correctness of surface levelling.
In an even different embodiment, the means for the levelling of the surface of the foamed plastic being deposited can take the form of a blower that would direct a stream of hot air onto the created structure. In such a configuration, it would be preferable to ensure means for measuring the correctness of surface levelling too, especially optical ones.
An additional, optional element of the device according to the invention may be a dye storage container or means for the supplying of dye from outside the device according to the invention. By supplying dye to the extruder sleeve (2, 103), the colour of the plastic being deposited can be modified, thus differentiating the structures being created by their intended use. For example, when creating a support/formwork intended for creating a topping beam for, e.g. a wide door, different shapes of such a support can be taken into account. The support (6) shown in
Such differentiation between the purposes of specific parts of foamed plastic structures can be used freely and accordingly to the needs—e.g. when creating formwork for a wall, some of the plastic can be planned to remain as thermal insulation or moisture separation. It is also possible to use more than one colour to differentiate between more than two groups of structures—e.g. to indicate which structure is to be removed after a week, which after two weeks, and which after three.
Therefore, the extruder sleeve (2, 103) may be connected to a dye storage container/means for the supplying of dye from outside the device that will ensure the supply of one, two, three, four, or five dyes/paints/colours. Depending on the needs, an expert will be able to select the type of dye and the means for its delivery, using vibratory conveyors for dyes in powder form, or tanks with pumps/valves etc. for liquid dyes.
An additional, optional element of the device according to the invention may be a solvent spraying assembly. This assembly can constitute an important element of the device, especially when, e.g., it is necessary to ensure proper roughness/smoothing of the surface of the foamed plastic structures, or to increase adhesion between adjacent layers. Said assembly can take the form of any prior art means for the controlled spraying of substances, e.g. an atomizer combined with a solvent container and a pump.
An additional, optional element of the device according to the invention may be an air supplying assembly, especially with means for the heating and (possibly) cooling of the air stream. Such an assembly can speed up the hardening of foamed plastic structures, when the foamed thermoplastic material escaping from the extruder nozzle (106) is blown on with cool air. On the other hand, blowing with a hot stream of air can slow down the hardening process of the thermoplastic material while also smoothing the surface of the created support/formwork/structure.
Yet another optional, additional element of the device according to the invention can be a separation layer depositing assembly, especially in the form of a powder storage container and a vibratory conveyor, or a powder/liquid atomizer, especially a pneumatic one. This assembly would be supposed to create a layer which, for example, would make it easier to separate a given foamed plastic structure from any adjacent structures—be they made of concrete or other materials. The material that the separation layer consists of can be in powder (e.g. mineral aggregate) or liquid form (e.g. paint or lacquer).
With regard to the method for the creating of structures according to the invention, the supports and formworks are made of foamed plastics using the incremental technique. The material supplied to the device is plastic in pellet form, preferably polystyrene, which is taken from the storage container and plasticized at an increased temperature by the screw that rotates inside the heated sleeve. The sleeve has nozzles that supply a compressed blowing agent such as carbon dioxide, nitrogen, or another gas, liquid (e.g. fluoro-hydrocarbons, compressed freon), or supercritical liquid chemically inert to the plastic being foamed. The blowing agent is mixed with the plastic, after which the former partly dissolves and partly takes the form of small bubbles. The sleeve is ended with a tapered nozzle. As the mixture passes through the nozzle, the plastic gets physically foamed by the blowing agent dissolved in it, as well as by the expansion of the bubbles of the blowing agent. The expansion of the gas (or the supercritical liquid, e.g. in the case of carbon dioxide) also results in the rapid cooling of the foamed plastic being pushed out of the nozzle. If the blowing agent is a liquid which is a gas at room temperature and under atmospheric pressure, then, during the passage through the nozzle, the liquid mixed with the plastic boils consequently foaming the plastic with the thus created bubbles.
After the introduction of the blowing agent, and before being pressed out, the mixture may pass through an additional mixing chamber.
It is preferable to achieve a high pressure in the foaming part of the extruder, which pressure would allow to use a supercritical liquid as the blowing agent. It is obvious that, depending on the selected plastics and blowing agents, the pressures may vary—the range of the achieved pressures is from 1 to 250 bar, preferably from 3 to 200 bar, and, the most preferably, from 5 to 150 bar. For example, for carbon dioxide, the pressure is at least 73 bar.
The material is laid by means of the manipulator in a manner similar to that used in incremental FDM techniques—the foamed plastic comes out of the nozzle in a plastic state, and bonds with the base or with the previous layers. After a layer of the desired thickness has been laid (constant thickness for the whole layer, or variable thickness on its surface), the depositing of the next layer begins.
After the supports have been created, subsequent layers of the building are deposited in the incremental technique, possibly together with reinforcement. After the concrete has been hardened, the supports are fragmented and then crushed e.g. with a briquetting machine, in order to reduce the porosity, and fragmented for reuse.
It is preferable to replenish the stored pellets located above the device by means of pneumatic transport.
It is important to achieve the lowest possible waviness of the support's surface. Therefore, after the support/formwork/structure has been created, means for the levelling of the surface of the plastic are used, e.g., cutting, grinding, smoothing, melting by contact with a hot tool, radiation, or blowing with hot air.
The support-printing head can also be used to create the thermal insulation of a building. In this case, the deposited material can be inside or outside the concrete structure, and this material is not removed at the end of the building process.
Since the process for removing the supports is not always fully automated, it is preferable to make it easier to separate the support from the surface of the concrete. The separation can be made easier by spraying a separation layer onto the last layer of the support, using an integrated spraying head. The separation layer can be, for example, wax or water-soluble polyvinyl alcohol. In another preferable embodiment, the separation layer can be created by the depositing of dust or powder, e.g. mineral aggregate. Various types of paints and lacquers with smooth surfaces, which do not adhere to concrete, can be used as the separation layer too. A solvent can be sprayed in order to smooth the surface or to increase adhesion between layers.
In order to achieve faster hardening of the deposited foamed plastic, the device may have a nozzle that blows compressed air into the vicinity of the nozzle. A vortex tube may be applied in order to lower the temperature of the blown air. In order to increase adhesion, the surface of the support material in the vicinity of the nozzle may also be heated with hot air, which melts the layer being deposited—with the previous layer.
In order to adjust the physical properties of the supports/formworks/structures being created, it is possible to adjust the size of the bubbles of the plastic being foamed. By applying a higher pressure, the amount of gas dissolved in the plastic is increased (both gas dissolved in the liquefied plastic, and gas in the form of bubbles)—after leaving the extruder nozzle, this will cause the plastic to foam more, and the resulting bubbles solidified in the plastic will be larger. This will increase the share of gas in the structure being created, thus reducing its mass, but also reducing its strength. On the other hand, by applying lower pressure, smaller bubbles are obtained—therefore, there is a smaller share of gas in the structure and a larger share of the plastic itself which, in turn, may increase the mass of the structure and its mechanical strength. Thanks to the invention, it is possible to design and execute spatially complex structures, in which a part of the structure is created with the use of lower pressures (more durable parts, higher consumption of plastic) and another part with the use of higher pressures (less durable, lighter parts, less plastic-consuming), which would effectively consume less plastic than in the case of filling a given space with a uniform mass of foamed plastic, but which would achieve comparable or even better mechanical strength, necessary to support e.g. a ceiling that is being poured.
In contrast to the methods that involve chemical foaming of plastics, physical foaming makes it possible to:
Another optional aspect of the method according to the invention is to differentiate the purpose of individual parts of the structures being made of foamed plastics, by colouring the specific parts of the structure in a specific colour. By using a plastic of a single and, in principle, the same colour, it is not possible to easily indicate which part can already be removed and which cannot—the building art would suggest to wait until the poured concrete has hardened before removing any supports. However, when differentiating between the parts of foamed plastic structures using colours, it is possible, for example, to mark in red the particularly important elements that should not be removed too early (e.g. after less than a week), and—in yellow—elements which can be removed after only four days allowing earlier access to individual parts of the structure being created (be it for inspection purposes or to carry out further works). Due to the ability to create layers that would be useful after a structure has been erected (e.g. moisture separation layer, thermal insulation layer), it is possible to use practically any colours in combination with any type or purpose of the specific structure made of foamed plastic.
List of markings used in the drawing:
| Number | Date | Country | Kind |
|---|---|---|---|
| 427212 | Sep 2018 | PL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/068514 | 7/10/2019 | WO | 00 |
