FR2951986A1 - Concrete i.e. hemp concrete projection device for e.g. clothing and insulation of house, has mixing unit comprised of aggregate unit and binding unit, and distribution unit in transport pipe supported by exit opening - Google Patents

Abstract

The device has a mixing unit comprised of an aggregate unit (10) and a binding unit (20). A distribution unit (600) in a transport pipe is supported by an exit opening. The aggregate unit and the binding unit are led to a transfer screw (500) i.e. endless screw, to convoy aggregates such as hemp straw, flax straw and polystyrene chips, and a binder i.e. air binder, in a projection unit. A recycling unit (30) of the mixing unit includes a pallet that demolishes mixture of the binder and aggregate before transferring into the projection unit.

Description

Low density concrete spraying device. FIELD OF THE DISCLOSURE The field of the invention is that of construction and more particularly of low density concrete construction.

By low density concrete is meant here and throughout the rest of the description, a mixture of binder, including air binder, and aggregates, such as aggregates based on hemp straw, flax straw, beads polystyrene etc. More specifically, the invention relates to a low density concrete spraying device. The invention applies in particular, but not exclusively, to the projection of hemp concrete for the manufacture and insulation of new houses, the renovation of half-timbered walls or drowned wood frame, or the insulation by the inside and out of existing homes. 2. State of the Prior Art and Drawbacks Current ecological trends and sustainable development policies are encouraging building professionals to develop alternative construction methods and materials. Thus, it has now been demonstrated that the use of hemp hemp or hempwood in the manufacture of construction and insulation materials has many interests. The chènevotte has indeed very interesting specific characteristics: a low density, a high content of silica, a high porosity, a high water absorption capacity and particularly interesting insulating properties.

Especially the chènevotte is used in mixture with lime and binders specific for the manufacture of mortar, concrete of hemp, brick of hemp .... Hemp concrete is used as: - wall material in timber frame houses; - light and insulating screed; - insulating coating; - roof insulation mortar. While the uses of hemp concrete are extremely diverse, the hemp concrete processing methods all tend to reconcile at least some of the following objectives: - simplicity of mixing operations, the user having to be able to perform these operations with a number reduced operations, and each of these operations must be as easy as possible; - effectiveness of the dosage, the water intake to be as small as possible when mixing materials; - safety of the user, especially during projection operations; - speed, simplicity and low cost of manufacture.

Among the different known methods of implementation, a first method of implementation consists in mixing by means of a concrete mixer or a kneader, then manually applying the hemp concrete on a support or manually discharging the concrete between two banches. This method of implementation has several disadvantages.

The ergonomics of the process is not optimal. In fact, the user must: - transport the water and the materials near the mixing device, - introduce the water, the binder and the hemp granulates into the device in the order, - stay close to the device to monitor mixing and to avoid excessive mixing, - empty the device as soon as the mixture is homogeneous. It is understood that such a method of implementation requires heavy and complex handling, which is binding and time consuming.

In addition, the amount of mixing water used during such a method of implementation is not optimized. To overcome these drawbacks, low density concrete or guniteuse spraying machines have been specifically adapted. Such guniters allow hemp concrete to be sprayed dry, that is to say that the wetting of the aggregate / binder mixture is carried out shortly before the projection of the material. More specifically and as illustrated in FIG. 1, an installation 10 for hemp concrete spraying comprises a vertical axis mixer 200 which cooperates with a guniteuse 100.

The kneader 200 comprises a loading device 210, in which the user places a hemp bag 220 (about 20kg), two bags of binder 231 and 232 (each about 22kg) and a dose of recycled concrete 240 ( that is to say a dose of wet concrete residues from the previous projection). When the tank of the kneader 250 is 3/4 empty, the loading device 210 (towed by a winch) brings the raw materials (bag of hemp, binder, ..) to the top of the tank 250 before dumping into the mixer in operation. The mixture of raw materials is carried out dry. The dry mixture is then poured continuously into the silo 110 of the guniteuse by a chute 260.

The guniteuse 100 comprises a rotor 120 comprising vertical cells 122, arranged regularly at the periphery of the rotor 120. The rotor 120 rotates about a drive axis 121 substantially vertical with respect to the ground. Referring to Figure 1, each of the vertical cells 122 passes (each turn) in a loading chamber 130, so as to fill with the dry mixture, the dry mixture falling into the cell by gravity. Once filled, each cell passes into a compression chamber 140 connected to a compressor 170 by an air inlet pipe 160. The air then expels the dry mixture from the cell in a transport pipe 150.

The transport pipe 150 includes a wetting ring 180 for moistening the dry mix. The wetting ring 180 is provided at the outlet of the pipe. The water is conveyed to the wetting ring 180 via a water inlet pipe 182 and then escapes from the wetting ring 180 through peripheral holes 181.

The hemp concrete then obtained is projected by a projection lance 191 mounted integral with the outlet of the transport pipe 150. The projection lance 191 comprises a tap 192, allowing the user to adjust the flow of water flowing in. the water inlet pipe 182, and thus to adjust the amount of water injected into the mixture as it passes through the wetting ring 180.

This conventional installation combining a guniteuse with vertical axis mixer represented an important progress in the hemp concrete spraying mechanism. Notably thanks to its improved ergonomics. However, it has a number of disadvantages. First, the hemp concrete obtained at the outlet of the mixer is not homogeneous. Such a lack of homogeneity is related on the one hand to the fact that mixing is carried out in successive batches and on the other hand by the fact that in the mixer used, the quantity of materials is not the same in function the position of the mixture in the tank of the mixer 250. Or the projection of a non-homogeneous mixture, for example on a wall, is at the origin of variations in mechanical strength within the wall. Another disadvantage of this technique of the prior art is related to the constitution of hemp concrete itself. Indeed, as has been previously described, hemp concrete is a mixture of lime and chenevotte granules. The presence of chenevotte gives the mixture a constitution called "strawberry" which impedes the fluidity of the flow in the chute 260 and thus the filling of the vertical cells 122 of the rotor 120 of the guniteuse. The filling rate of the cells is therefore not controlled. This results in an air consumption higher than that which would be necessary to empty the cells. Indeed, to avoid any risk of jamming, particularly at the connecting elbow (at 90 °) between the outlet of the compression chamber 140 and the inlet of the transport pipe 150, the user is required to adjust the flow The air supply provided by the compressor 170. This assumes that each load a cell filled with hemp concrete, which is rarely the case. Air consumption is not optimized.

It is also noted that the wetting of the mixture is not optimal. Indeed, as for the air flow, the user must make a setting of the wetting rate which is only adapted to a given amount of mixture to humidify. However, in use, the amount of mixture to be moistened varies with the rate of filling and emptying cells.

In addition, as already indicated, to be hydrated the hemp concrete passes through a curtain of water generated by a mooring ring 180 located about 3 meters upstream of the outlet of the transport pipe 150. This curtain d Water consists of jets from the periphery of the ring, dry hemp concrete passes through this curtain of water. The low density of the hemp concrete particles causes the radiant jets to disturb the flow and sediment the aggregates by slowing down their travel. Furthermore, to ensure airtightness of the cells and limit dust emissions, the rotor 120 of the guniteuse rotates between two rubber discs. Another major disadvantage of this known installation lies in the fact that the guniteuse requires a large electrical power to compensate for friction between the rotor and the rubber discs. The inventors have furthermore found that the rubber discs should be replaced fairly regularly due to wear. In order to overcome these drawbacks, the Applicant proposes in its patent application FR 2 915 702 a low density concrete spraying device, represented in FIG. 2 and which comprises: means for conveying an air flow under pressure cooperating with a transport pipe comprising an output projection lance; - Kneading means (500) horizontal axis of a first material (M3), called binder, and a second material, called granulate; distribution means (600) for a mixture of binder and granulate obtained at the outlet of said mixing means (500), said dispensing means (600) comprising a substantially horizontal dispensing duct (601) connecting said conveyor means at the inlet of the transport pipe, and receiving said mixture; - A casing (700) defining a substantially closed chamber, and accommodating said mixing means and said dispensing means, and in that the central axis of the mixing means is substantially perpendicular to the central axis of the dispensing means.

According to the device described in the patent application FR 2 915 702, the mixture at the outlet of the mixing means falls by gravity into a metering lock comprising a plurality of U-shaped cells. Each cell alternately passes, depending on the rotation of the device. the lock, between a loading position in which the mixture is loaded into the cell and an unloading position in which the mixture is discharged from the cell into the distribution duct. The mixing and distribution of materials are carried out in horizontal planes, which reduces the risk of clogging at the bent portion and improve the homogeneity of the mixture. In addition, the integration of the mixing and dispensing means in closed and impermeable enclosures makes it possible to reduce dust emissions and to ensure that the mixture of materials remains dry. However, the Applicant observed during the implementation of such a device that the dispensing means and in particular the metering lock can wear relatively quickly.

This wear is essentially linked to the "straw-straw" nature of hemp concrete, which causes shearing forces acting on the metering lock during its operation and which tend to accelerate the wear of the lock. . Another disadvantage related to the "straw" nature of hemp concrete is that such a constitution tends to increase the risk of jamming and clogging of the device, particularly at the level of the metering lock. These two phenomena are able on the one hand to accelerate the wear of the device and on the other hand to be at the origin of a lack of homogeneity of the projection of hemp concrete. Indeed, as for the device of the prior art described in Figure 1, the filling rate of the cells of the lock is not controlled. Such a lack of homogeneity results in a non-optimal consumption of the device in air, water and energy unless these parameters are continuously regulated as a function of the mixture of each cell, which greatly complicates the device. Thus, because of the problems of wear, clogging and stuffing described above, such a device requires the regular implementation of relatively complex and expensive maintenance operations. However, the frequency and duration of these operations are not always consistent with the time and cost of construction sites. 3. Objectives of the invention The object of the invention is to overcome the drawbacks of the prior art.

More specifically, an object of the invention, in at least one of its embodiments, is to provide such a device that reduces the risk of clogging and stuffing inside the device. Another object of the invention, in at least one of its embodiments, is in particular to provide a low density concrete spraying device which makes it possible to improve the homogeneity of hemp concrete as well as the homogeneity of its composition. projection. Another objective of the invention, in at least one of its embodiments, is to provide such a device that makes it possible to optimize consumption of water, air and energy.

The invention, in at least one of its embodiments, also aims to provide such a device whose implementation, maintenance and maintenance are simpler and less expensive than the devices of the prior art. 4. Objective of the invention These objectives and others which will appear later are achieved with the aid of a low density concrete spraying device, in particular hemp concrete, comprising a mixing unit, a linear projection unit and a distribution means. The mixing unit comprises at least aggregate supply means and binder which open on a single transfer screw. The transfer screw is capable of conveying the aggregates and the binder into the projection unit which comprises means for conveying a flow of pressurized air and a transport pipe comprising at the output a projection lance. The conveying means is substantially aligned with the transport pipe. The transfer screw extends substantially perpendicular to the conveying means and the transport pipe. According to the present invention, the conveying means and the transfer screw open directly into the dispensing means respectively via a first inlet orifice and a second inlet orifice, the dispensing means opening directly into the transport pipe by means of a outlet port. Low density concrete is a concrete having a lower density than conventional concrete which is a mixture of cement, water, sand and gravel and whose density is in the range of 2.2 to 2 , 25 ton / m3. Low density concretes are obtained with aggregates with a lower density than sand. This is particularly the case with the hemp hemp which in combination with a binder (lime) forms hemp concrete whose density is of the order of 0.25 to 0.4 ton / m3. The aggregates and binder supply means are constituted by two separate hoppers, a hopper for hemp hemp granules and a hopper for the binder (lime). The aggregates and the binder are loaded at the top of their hopper and fall by gravity into the transfer screw which is provided at the bottom of the hoppers. The transfer screw extends under the hoppers in a substantially horizontal plane. It allows both the dosage of the aggregates and the binder and their transport to the dispensing means. The transfer screw opens directly into the dispensing means. The main axis of the transfer screw is essentially perpendicular to the main axis of the dispensing means. The conveying means of the pressurized air flow and the transport pipe are also directly connected to the dispensing means. The main axis of the conveying means, the dispensing means and the transport pipe are essentially aligned. The particular arrangement between the mixing unit and the projection unit, in particular between the transfer screw, the conveying means and the transport pipe, makes it extremely easy and inexpensive to solve problems related to the nature "Straw blower" of hemp concrete (problems of clogging and stuffing, defects in filling and expulsion of the cells) and thus to propose a low density concrete spraying device with optimized energy and water consumption and better homogeneity projection relative to known devices.

According to an advantageous embodiment, the transfer screw is a worm whose screw pitch at the level of the granulator feed means and the binder is greater than the screw pitch in the vicinity of the second feed orifice of the feed means. distribution. The implementation of such a screw makes it possible to generate a buffer or plug of materials at the inlet of the dispensing means. The density of the pad or plug of material formed is such that it allows on the one hand to manage the flow and homogeneity of the mixture of materials arriving at the dispensing means and on the other hand to prevent the pressurization of the material. mixing unit during the projection. The implementation of such a screw thus makes it possible to limit the wear of the transfer screw and to further optimize the energy consumption and water consumption of the projection device as well as its efficiency. According to a variant of this embodiment, the pitch of the transfer screw at the level of the aggregates supply and binding means is at least 30% less than the pitch of the screw near the second inlet orifice of the means of distribution.

According to a preferred embodiment, the screw thread of the transfer screw decreases along the entire length of the screw in a regular manner. Thus, in this embodiment, the decrease of the screw pitch between two successive threads is constant over the entire length of the screw.

According to another preferred embodiment, the thread of the transfer screw decreases along the length of the screw irregularly. In this embodiment, the reduction of the thread pitch between at least two successive threads is not the same over the entire length of the screw. Advantageously, the transfer screw is a screw with core.

The implementation of a screw without a core makes it possible for the plug of materials to be obtained only at the inlet of the dispensing means and not all along the transfer screw. The risk of clogging and stuffing at the mixing unit and the wear of the transfer screw are further reduced. Advantageously, the transfer screw has a length less than the length of the mixing unit. In this variant, a free space is left between the end of the transfer screw and its inlet of the dispensing means. The presence of this free space on the one hand promotes the formation of the material plug at the inlet of the dispensing means and on the other hand improves the quality of the plug formed.

According to a preferred embodiment, the mixing unit further comprises at its output at least one pallet able to undo a mixture of aggregates and binder before transfer into the projection unit. In this embodiment, pallets are provided at the inlet of the dispensing means to allow the material plug to be undone. The mixture of materials handled by the spraying unit is less compact, the transport of the mixture in the spraying unit is improved, the risks of clogging and stuffing are reduced. Advantageously, said pallet or pallets are inclined at an angle of 15 ° with respect to said transfer screw.

According to a variant of the invention, the mixing unit further comprises recycled feed means which are connected to a third inlet orifice of the dispensing means, close to the second inlet orifice of said dispensing means. .

The term "recycled" defines concrete residues from a previous projection. These residues are recovered and reintroduced into the device for a new projection. As for the aggregates supply and binder means, the recycled feed means comprise a hopper. The recycled is loaded from the top of the hopper. Advantageously, the recycled feed means comprise at least one pallet able to undo a mixture of aggregates and binder before it is transferred to the projection unit. In a preferred embodiment, the granule feed means comprises a hydrator. Such a hydrator is composed of a sprayer which is provided at the top of the aggregate hopper. This hydrator will create a very fine mist over chenevotte aggregates, moisturizing slightly the aggregates. Such hydration further improves the formation of the material plug at the inlet of the dispensing means. Preferably, the aggregates feed means comprise a horizontal axis agitator provided above the transfer screw. The axis of the agitator extends in the aggregate hopper substantially parallel to the axis of the transfer screw. The agitator when activated is rotated and agitates the granulate in the hopper. Such brewing makes it possible to make the flow of the granulate more regular, in particular when the aggregates are slightly hydrated. Such mixing also makes it possible to homogenize the hydration of the aggregates. The risk of clogging and jamming at the transfer screw is reduced thereby improving the performance of the projection device. 5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and nonlimiting example, and the accompanying drawings, among which: in Figure 1, already commented in connection with the prior art, presents the simplified diagram of a conventional installation for the projection of hemp concrete; FIG. 2 is a simplified schematic representation of a projection device described in patent application FR 2 915 702; - Figures 3 to 4 show a projection device according to one embodiment of the invention. 6. DETAILED DESCRIPTION OF THE EMBODIMENT The general principle of the invention is based on the implementation of a mixing unit allowing essentially horizontal mixing and a linear projection unit in which the conveyor means of the The spraying unit and the transfer screw of the mixing unit open directly into the dispensing means, the dispensing means opening directly into the transport pipe.

The device according to the present invention makes it possible to reduce in a very simple and inexpensive way the risks of clogging in the device are reduced, the transport of the concrete is essentially linear, more fluid and more homogeneous which makes it possible to improve the homogeneity of projection and optimize the energy and water consumption of the device.

One embodiment of a low density concrete spraying device according to the present invention is described in more detail in FIGS. 3 to 4. The description of the embodiment shown in FIGS. 3 to 4 is given by way of nonlimiting illustration. The device shown comprises a mixing unit.

The mixing unit comprises: - a first hopper 10 designed to receive hemp granules; a second hopper 20 designed to receive lime; - A third hopper 30 provided to receive recycled concrete projections.

The mixing unit further comprises a transfer screw 500 extending substantially horizontally under the first and second hoppers. In the embodiment shown, the first hopper 10 has a capacity of 400 L, the second hopper 20 has a capacity of 150 L and the third hopper 30 has a capacity of 100L.

The first hopper 10 has at its upper part a hydrator and in the middle part a stirrer 15 with a horizontal axis. The agitator 15 includes "fingers" that pass over the transfer screw. I1 is connected to a motor means 12 capable of rotating it.

In a particular embodiment, a similar stirrer 25, 35 may be provided in the middle part of the second and / or third hopper respectively. The first hopper 10 and the second hopper 20 open into the transfer screw 500. The transfer screw 500 is a worm having a core 75 mm in diameter. The first five steps of the screw are 160 mm, the four intermediate steps are 180 mm and the last three steps are tightened and are respectively 160 mm, 150 mm and 140 mm. The last turn of the screw is 320 mm from the inlet of the dispensing means. The transfer screw 500 is connected to a motor means 12 capable of rotating it. The hemp granules and the lime arriving at the transfer screw 500 are supported by the transfer screw 500 which transports them to the dispensing means 600. At the junction between the transfer screw 500 and the dispensing means 600 three vanes extending substantially vertically with respect to the main axis of the transfer screw 500 are provided at an angle of 15 °. These pallets are 30 mm wide and 65 mm high. Their thickness is 8 mm. Each of these pallets has a bevelled face capable of undoing the material plug which is formed at the junction between the transfer screw 500 and the dispensing means 600. The transfer screw 500 may be inclined at an angle α less than 90 ° in relation to the ground. In the embodiment shown, the angle α is 10 °. With such an inclination of the transfer screw 500, the mixture tends to return back by gravity, which increases the contact time of the material mixture with the transfer screw 500, thus promoting the homogeneity of the mixture. The transfer screw 500 is secured at each of its ends to a structural element for laying and holding the device 14, 23, 13 on the ground. As has been described previously, a horizontal axis stirrer 25 may be provided in FIG. second hopper 20. Advantageously, the axis of the agitator 25 has an angle of inclination less than 90 ° with respect to the ground and is capable of transporting the binder from bottom to top towards the transfer screw 500.

Such a conformation makes it extremely easy to regulate, as a function of the angle of inclination, the displacement of the binder towards the transfer screw 500. The homogeneity of the mixture is improved. The first 10 and second hoppers are aligned along the transfer screw 500.

The third hopper is slightly offset from the axis of the transfer screw 500. It opens into the dispensing means 600 via a stirrer 35 horizontal axis. The projection unit comprises a conveying means of a flow of air under pressure and a transport pipe comprising an output projection lance. The main axis of the conveying means and the main axis of the transport pipe are essentially aligned. The dispensing means 600 joining the mixing unit to the projection unit forms a chamber and has: an inlet port connected to the conveying means, an inlet port connected to the transfer screw, a inlet port connected to the agitator of the recycled hopper, an outlet port connected to the transport pipe. In the embodiment shown, the air flow thus arrives at the top of the dispensing means 600 for conveying the material mixture downwardly from the dispensing means into the transport pipe. 7. Operation of the device according to the described embodiment The slightly hydrated granulate and the binder are transported by the transfer screw to the dispensing means. During transport, a mixture of materials is formed and a plug of material is obtained at the inlet of the dispensing means. The pallets will then undo the plug material to make it less compact before entering the dispensing means and facilitate its transport in the projection unit. The mixture of uncompressed material arriving in the dispensing means 15 is driven by the flow of air from the conveying means into the transport pipe where it is hydrated to give the hemp concrete. The concrete obtained is driven by the air flow to be projected by the projection lance.

Claims (13)

REVENDICATIONS1. A low density concrete spraying device, in particular hemp concrete, comprising a mixing unit (10; 20; 30), a linear projection unit and a distribution means (600), said mixing unit comprising at least means for supplying aggregates (10) and binding agent (20), said means for supplying aggregates (10) and binder (20) leading to a single transfer screw (500) capable of conveying the aggregates and the binder in said projection unit, said linear projection unit comprising means for conveying a flow of pressurized air and a transport hose comprising at the output a projection lance, said conveying means being essentially aligned with said transport pipe and said transfer screw extending substantially perpendicular to said conveying means and said transport pipe, characterized in that said conveying means and said transfer screw open directly into said dispensing means respectively by a first inlet port and a second inlet port, said dispensing means (600) opening directly into said transport pipe through an outlet port. 2. Device according to claim 1 characterized in that said transfer screw (500) is a worm whose screw pitch at the level of the granules supply means (10) and binder (20) is greater than the pitch screw near the second inlet of said dispensing means. 3. Device according to claim 2 characterized in that the pitch of said transfer screw (500) at the level of the aggregates supply means (10) and binder (20) is at least 30% less than the step of the screw near the second inlet of said dispensing means. 4. Device according to claim 2 or 3 characterized in that the thread of said transfer screw (500) decreases along the entire length of the screw in a regular manner. 5. Device according to claim 2 or 3 characterized in that the thread of said transfer screw (500) decreases along the length of the screw irregularly. 10 6. Device according to any one of claims 2 to 5 characterized in that said transfer screw (500) is a screw with core. 7. Device according to any one of claims 2 to 6 characterized in that said transfer screw (500) has a length less than the length of said kneading unit. 8. Device according to any one of the preceding claims characterized in that said mixing unit (10; 20; 30) further comprises at its output at least one pallet able to undo a mixture of granules and binder 20 before its transfer. in the projection unit. 9. Device according to claim 8 characterized in that said pallet or pallets are inclined at an angle of 15 ° relative to said transfer screw. 25 30 15 10. Device according to any one of the preceding claims characterized in that said mixing unit (10; 20; 30) further comprises recycled feed means (30) and in that said feed means recycled (30) are connected to a third input port of said dispensing means near the second inlet port. 11. Device according to claim 10 characterized in that said recycled feed means (30) comprise at least one pallet able to undo a mixture of aggregates and binder before transfer into the projection unit. 12. Device according to any one of the preceding claims, characterized in that said granule feeding means (10) comprise a hydrator. 13. Device according to any one of the preceding claims characterized in that said aggregates supply means comprise a horizontal axis agitator provided above said transfer screw.