DEVICE FOR STORING AT LEAST ONE BULK ITEM

Description

[0001] The invention relates to a storage device for at least one bulk material comprising a force sensor. More particularly, the invention relates to a storage device for at least one bulk material enabling the determination of the fill level of said container.

[0002] Large bulk containers (IBCs) also commonly referred to as "IBC" containers (for « Intermediate Bulk Container » Bulk containers are used in many fields such as the chemical, pharmaceutical, food processing, cosmetics, and medical industries. The most common large bulk containers have a capacity of approximately 1,000 L. They can contain various types of liquid products such as water, organic solvents, paints, hazardous chemical residues, food raw materials, or beverages, or powdered products such as raw materials in pellet form, food powders, cereals (rice, wheat grains, etc.), or agricultural seeds.

[0003] The filling level or filling rate of such large bulk containers is generally controlled empirically by operators and does not allow for optimal anticipation of stock management and quantities of products available, nor for avoiding any stockouts.

[0004] Ultrasonic sensors have been proposed for placement inside a container to determine its fill level. However, the reliability of such sensors is compromised, particularly by exposure to the product inside the container.

[0005] A device according to CN207312306U is known, comprising a container for holding a liquid, a rectangular frame, and a support with four force sensors arranged under the container to determine its total weight and variations. The container rests solely on the four force sensors, and its base is offset from the frame. The device according to CN207312306U also includes a memory containing the nature of the liquid inside the container.

[0006] WO 2005 / 037668 also discloses a tobacco container comprising a weighing device for determining the weight of the tobacco in the container. The weighing device includes load cells or pressure sensors.

[0007] We also know of CN 103625736 a storage trolley comprising an upper platform and a lower platform, the upper platform having a slot fitted with a weighing instrument allowing the total mass of the products placed on the trolley to be determined.

[0008] However, such containers equipped with these devices are expensive and cannot be used on an industrial scale for all types of products or industries, particularly in the field of bulk material transport. In particular, devices adapted for weighing around 1,000 liters of bulk material, sometimes exceeding one ton, are especially costly.

[0009] The invention aims to overcome these drawbacks.

[0010] The invention aims in particular to provide an inexpensive device for determining a representative data point of the filling rate of a container.

[0011] It also aims to offer such a device whose handling, storage, transport, packaging and installation are simple, do not require special precautions, can be carried out by non-specialized operators, and do not in any way risk affecting the performance of the force sensor.

[0012] It also aims to offer such a device that is resistant to the external environment, in particular to humidity or chemical or mechanical aggressions, as well as to temperature variations.

[0013] The invention therefore relates to a storage device for at least one bulk material according to claim 1.

[0014] In other words, the weight of the bulk material in the container depends only partially on the force sensor(s) (i.e., only partially on all of said force sensors) and in no way solely on a set of force sensors. A device according to the invention is therefore distinct from a device for measuring the total weight of a material contained in a container (or the total weight of a container with or without its contents).

[0015] The said force measuring device may include one or more force sensors (and includes in particular all force sensors located under the bottom of the container and in contact with the bottom of the container of the storage device).

[0016] In a storage device according to the invention, the single force sensor or set of force sensors of said force measuring device, each force sensor being located under the bottom of said container and in contact with said bottom, is not subjected to the total weight of the bulk material introduced into said container. The bottom of said container therefore also rests on at least one support, such support being separate from the container and thus from the bottom of the container.

[0017] The inventors found that using a force sensor on which the container only partially rests was sufficient to reliably determine the container's fill level and / or the change in that fill level. In particular, a storage device for at least one bulk material according to the invention allows for a simplified and economical determination of the container's fill level and / or its change, without needing to measure the total weight of the bulk material contained in the container. Such a measurement of the total mass (or total weight) necessarily implies that the entire weight of the bulk material introduced into the container is borne solely by the weighing mechanism of that device.

[0018] The device according to the invention is placed on a support, said support being subjected to the weight of said bulk material introduced into said container and to the weight of said container, the container also resting on said support. In accordance with the invention, said device comprises a support having an upper face for receiving the bottom of said container, the bottom of the container, the support, and each force sensor being arranged such that at least a portion of the bottom of the container is supported in direct contact with the upper receiving face, said upper receiving face being adapted to be subjected, at least in part, to the weight of said bulk material introduced into said container.

[0019] According to the invention, each force sensor is disposed between the bottom of said container and said support so that the support is subjected at least partially to the weight of said bulk material introduced into said container, each force sensor being subjected only partially to the weight of said bulk material introduced into said container.

[0020] A force sensor on which said container only partially rests, said container also resting on a support (distinct from said force sensor), is sufficient to allow a reliable determination of the filling rate of said container and / or the variation in the filling rate of said container.

[0021] Throughout the text, "top" and "bottom," and the terms "superior" and "inferior," are defined in relation to Earth's gravitational field. Specifically, with the container placed on the support, an element located at the top is on the side of the container and an element located at the bottom is on the side of the support.

[0022] Throughout the text, the expressions "a force sensor" or "said force sensor" apply to each force sensor of a force measuring device of a storage device according to the invention. Each force sensor can be disposed at any location on the upper receiving face, in particular substantially below the center of the bottom of the container or between any peripheral edge of the lower face of the container (i.e., the bottom) and its center.

[0023] The container may contain a material suitable for flowing like a liquid, that is to say, a material chosen from the group consisting of liquids and powdered materials (powdered solids in particular). Such materials are also called "bulk" materials.

[0024] A force sensor used in a storage device according to the invention is autonomous, is not in contact with the contents of the container and is resistant to the transport conditions of said containers, to their washing or cleaning, to heat (for example to temperatures up to 90°C).

[0025] In certain embodiments according to the invention, each force sensor comprises at least one sensitive element whose electrical characteristic varies according to a force exerted by said container on said force sensor.

[0026] In some embodiments according to the invention, each force sensor includes at least one strain gauge.

[0027] A strain gauge (generally improperly referred to as a "strain gauge") has at least one electrical characteristic (usually resistance or capacitance) which varies according to a state of deformation of the surface of a solid on which said strain gauge is placed.

[0028] In certain embodiments according to the invention, each force sensor comprises a housing incorporating two strain gauges and a deformation element, the two strain gauges being fixed to said deformation element. In certain embodiments according to the invention, the housing of said force sensor is formed of a rigid material.

[0029] In certain embodiments according to the invention, each strain gauge has at least one electrical characteristic that varies according to its deformation, the force sensor being arranged such that the electrical characteristic varies according to a deformation state of the strain element. The strain element can take various forms, for example, the form of a plate, a strip, a beam, a rod, or a spiral winding. The strain element can be made of at least one material selected from the group consisting of metallic materials, polymer materials, ceramic materials, and their composites.

[0030] In certain embodiments according to the invention, said storage device according to the invention comprises an electronic circuit: electrically connected to each strain gauge, adapted to measure said electrical characteristic of each strain gauge, and to deliver a signal, called measurement signal, representative of said electrical characteristic of each strain gauge.

[0031] Each strain gauge of a force sensor according to the invention has electrical connection pads allowing this strain gauge to be electrically connected to an electronic circuit adapted to measure said electrical characteristic of the strain gauge.

[0032] Each force sensor according to the invention can have all shapes and dimensions, depending on the applications, and in particular depending on the number of sensitive elements and their nature.

[0033] In some possible embodiments, a force sensor according to the invention has a disc shape, with a diameter of approximately 1 cm to 5 cm, particularly approximately 2 cm to 3 cm. The force sensor may also have a generally parallelepiped shape with a width greater than 0.5 cm—in particular less than 10 cm, for example approximately 1 cm to 3 cm—and a length greater than 2 cm—in particular less than 20 cm, for example approximately 2 cm to 8 cm. All other shapes (segment of a cylinder, cap, prismatic, non-remarkable shape, etc.) and dimensions are possible.

[0034] In certain embodiments according to the invention, said force sensor has a smaller dimension, i.e. a thickness, between 1 mm and 15 mm.

[0035] In certain embodiments according to the invention, each force sensor has a substantially flat upper face, referred to as the contact face, said contact face being adapted to be able to make contact with said lower face of the container. In certain embodiments according to the invention, said contact face of each force sensor (upper face of the force sensor housing) is adapted to be able to act on the deformation element of said force sensor (optionally by means of a piston disposed inside said force sensor, between the contact face of the force sensor and said deformation element).

[0036] In certain embodiments according to the invention, each force sensor has a mounting face adapted to allow the force sensor to be fixed to the receiving face of the support.

[0037] The mounting face can be any shape and is adapted to the shape of the solid surface to which the sensor is to be attached. In particular, the mounting face can be flat. Alternatively, the mounting face can be a skewed surface, for example, cylindrical, a cap, a polyhedral surface, or other. Thus, the mounting face can be chosen, for example, from the group consisting of flat faces, concave cylindrical faces (especially cylindrical faces of revolution), convex cylindrical faces (especially cylindrical faces of revolution), concave spherical caps, convex spherical caps, concave paraboloid caps, convex paraboloid caps, concave polyhedral faces, and convex polyhedral faces. The mounting face can also have any unremarkable skewed shape, neither convex nor concave.

[0038] The said force sensor can be assembled (glued and / or screwed for example) to the support and / or to the bottom of the container or simply positioned between the support and the container (before or after placing the said container in or on the support).

[0039] In certain embodiments according to the invention, the device includes an electric accumulator. In certain embodiments according to the invention, each force sensor is connected to a secondary electronic unit comprising at least one electric accumulator (for example, a cell or battery) and an electronic circuit board connected to said accumulator. This secondary electronic unit may also include a wireless communication module. Such a secondary electronic unit has the advantage of reducing the size of the force sensor, as the secondary electronic unit can be positioned on the side of the container, on its upper surface, attached to the support, or integrated into the container or support, while being connected to said force sensor by a cable.

[0040] Alternatively, each force sensor can comprise a housing that also includes the battery, the electronic board connected to the battery, and the wireless communication module, eliminating the need for a separate electronic housing. A single housing containing the force sensor is then placed under the bottom of the container.

[0041] In certain embodiments according to the invention, said device includes a wireless communication module. Such a communication module can enable the transmission and / or reception of any data relating to the container (its volume, its shape, etc.), the nature of the bulk material contained in the container, the temperature, the fill level of said container, etc.

[0042] Such a wireless communication module can be chosen, for example, from a radio frequency communication module, an infrared communication module, an optical communication module, a magnetic communication module, or an inductive communication module. Advantageously, it can be a radio frequency module enabling the transmission of the measurement signal according to any appropriate radio frequency protocol (Wi-Fi®, Bluetooth®, ZigBee®, SigFox®, LoRaWAN®, mobile telephony protocol (GPRS, UMTS, LTE, WiMax...)).

[0043] In certain embodiments according to the invention, each housing of the device can be formed of at least one polymeric material, for example, chosen from the group consisting of polyimide, polyolefins (in particular polyethylene (PE) - in particular high-density polyethylene (HDPE) or low-density polyethylene (LDPE) - poly(ethylene terephthalate) (PET), polypropylene (PP), polyethylene naphthalate (PEN), and cyclo-olefin copolymer (COC)), polymethyl methacrylate (PMMA), polycarbonate (PC), polyetheretherketone (PEEK), poly(vinyl chloride) (PVC), acrylonitrile butadiene styrene (ABS), and halocarbon polymers (in particular fluorocarbons such as polytetrafluoroethene (PTFE) and poly(vinylidene fluoride) (PVDF)).

[0044] The force measurement device may include one or more force sensors. In certain embodiments according to the invention, said force measurement device comprises a single force sensor. Although a single force sensor is sufficient to reliably determine the fill level of said container or its variation, there is nothing preventing the force measurement device from comprising several force sensors, for example, two, three, four, or even five or more force sensors (identical or different from one another, preferably identical). A storage device according to the invention comprising a force measurement device with at least two force sensors makes it possible, in particular, to increase the accuracy of the fill level determination.

[0045] Various embodiments can be envisaged with regard to the container of a device according to the invention, particularly its size and shape. The container may have a parallelepiped, cubic, cylindrical, or more complex intermediate shapes, such as a container in the form of four cylinders placed side by side. In some embodiments according to the invention, said container has a generally cubic shape. The support associated with each container may also take various forms. A cubic container may, for example, be arranged inside a support that is itself cubic (or one or two portions of a cube) of slightly larger dimensions. The support may take the form of a tray receiving only the lower part of the container and may have a conjugate shape to such a container, which itself may have any of the aforementioned shapes.

[0046] In certain embodiments according to the invention, said container has a maximum capacity of between 5 L (0.005 m 3< ) and 5000 L (5 m 3< ), in particular between 50 L (0.05 m 3< ) and 2000 L (2 m 3< ), notably between 100 L (0.1 m 3< ) and 1500 L (1.5 m 3< ), and more particularly between 500 L (0.5 m 3< ) and 1200 L (1.2 m 3< ).

[0047] In certain embodiments according to the invention, said container has an opening adapted to allow the introduction of said bulk material into said container. For example, it may be an opening fitted with a screw-on cap.

[0048] In certain embodiments according to the invention, said container is formed of at least one material selected from the group consisting of metallic materials, polymer materials, cellulosic materials, and composite materials. In certain embodiments according to the invention, said container is formed of at least one polymer material selected from the group consisting of thermoplastic polymers and thermosetting polymers.In particular, the container of a device may be formed of at least one polymeric material, for example chosen from the group consisting of polyimide, polyolefins including polyethylene (PE) - in particular high-density polyethylene (HDPE) or low-density polyethylene (LDPE) - poly(ethylene terephthalate) (PET), polypropylene (PP), polyethylene naphthalate (PEN), and cyclo-olefin copolymer (COC)), polymethyl methacrylate (PMMA), polycarbonate (PC), polyetheretherketone (PEEK), poly(vinyl chloride) (PVC), acrylonitrile butadiene styrene (ABS), and halocarbon polymers (in particular fluorocarbons such as polytetrafluoroethene (PTFE) and poly(vinylidene fluoride) (PVDF)).

[0049] The container is made of a suitable material to allow its base to be in contact with both the upper surface of the force sensor and the support. This is the case for all large bulk containers, given the small thickness of a force sensor compared to the dimensions of large bulk containers. In certain embodiments according to the invention, the container has a base made of at least one flexible material. In particular, the base of the container is made of a material more flexible than that of the force sensor (or, in particular, than the material of the force sensor housing). In this way, the base conforms to the shape of the force sensor housing to make contact with the support. However, there is also nothing to prevent the use of a container with a rigid base (in particular, one at least as rigid as the force sensor housing).In the latter case, care must be taken to ensure that the rigid base of the container is also in contact with the support, in particular by avoiding placing the force sensor under the center of said base.

[0050] Other objects, features and advantages of the invention will become apparent from the following description, given by way of non-limiting example, of some of its possible embodiments and which refers to the accompanying figures in which: there figure 1 is a schematic perspective view of a device according to a first embodiment of the invention, the figure 2 is a schematic perspective view of the device of the figure 1 in which the container was removed, the figure 3 is a diagram of the force sensor and the secondary electronic housing of a device according to the invention, the figure 4 is a schematic perspective view of the interior of a force sensor of a device according to the invention, the figure 5 is a schematic cross-sectional view of a device according to a second embodiment of the invention, the figure 6 is a diagram illustrating a result of the filling rate of a container of a device according to the invention.

[0051] In the figures, the scales are not necessarily respected, particularly in thickness, for illustrative purposes.

[0052] The device according to the first embodiment of the invention shown in figures 1 à 2 understand : a container 10 into which said bulk material selected from the group consisting of liquids and powdered materials can be introduced, said container having a base adapted to be able to bear the weight of a bulk material introduced into the container, a force measuring device comprising a single force sensor 1 disposed under the base of the container 10 and in contact with said base, so as to be subjected only partially to the weight of said bulk material introduced into said container, a support 16 having an upper face 18 for receiving the container 10 adapted to be able to bear at least partially the weight of the bulk material introduced into the container.

[0053] In this first embodiment, the container 10 and the support 16 form a large bulk container of the type comprising a support 16 in the shape of a pallet, allowing the device to be handled by a forklift. The support 16 is also accompanied by a wire mesh structure 17 (or wire mesh cage) adapted to receive, protect, and mechanically reinforce the container 10. The wire mesh structure 17 is generally metallic, and the pallet-shaped base of the support 16 can be made of polymer material, wood, metal, or a polymer matrix composite material.

[0054] The container 10 has a generally cubic shape. The container 10 has an opening 12 formed by a screw-on cap adapted to allow the introduction of the bulk material into the container, the opening 12 being located on the upper face 11, opposite the bottom of the container. The container 10 shown also includes a liquid outlet in the form of a valve 14 provided at the bottom of one side face of the container.

[0055] In this first embodiment of a storage device according to the invention, the force measurement device comprises a single force sensor 1. A single force sensor, on which the container only partially rests, is sufficient to allow for a reliable determination of the container's fill level and / or a change in the container's fill level. However, there is nothing preventing the force measurement device from comprising several force sensors, for example, two, three, four, or even five force sensors (identical or different, preferably identical). The use of a force measurement device comprising at least two force sensors increases the accuracy of the fill level determination by, for example, performing a double or triple measurement of the container's fill level for comparison.

[0056] The force sensor 1 is positioned in contact with the lower face of the container (forming the bottom of the container) and outside the container. The force sensor 1 has a substantially flat upper contact face adapted to make contact with said bottom of the container 10. The force sensor 1 has a lower mounting face adapted to allow the force sensor to be fixed to the upper receiving face 18 of the support.

[0057] In the first embodiment shown, as can be seen in the figure 2 , the force sensor 1 is positioned substantially below the center of the bottom of the container 10. However, nothing prevents it from being positioned at any other location between the bottom of the container and the support, as long as the force sensor 1 is positioned substantially entirely below the bottom of the container and on the receiving face of said bottom of the support.

[0058] The force sensor 1 is electrically connected by a cable 2 to a secondary unit 3 comprising a battery (battery 4) and an electronic board 5 connected to the battery 4. The electronic board 5 consists of a module for acquiring the electrical signal from the force sensor 1 and a wireless communication module capable of transmitting the data, for example, over a low-power wireless network (also known as LPWAN). The secondary electronic unit 3 also includes an antenna 6.

[0059] There figure 3 is a schematic representation of the force sensor 1 and the secondary housing 3 electrically connected to each other.

[0060] The data collected includes, for example, location, temperature, or the state of the tank (empty / full, dirty / clean...).

[0061] This data is sent, for example, with a frequency of one hour. The data sending frequency, the ON / OFF periods of force sensor 1, and the alert thresholds can be configured remotely.

[0062] There figure 4 This is a schematic representation of the components of force sensor 1. Force sensor 1 includes an external housing (not shown in figure 4 ) incorporating two strain gauges 24, 25 coated with a resin 29, a strain element 20, a base 21 on which the strain element 20 rests, and a piston 22 capable of transmitting a force (symbolized by the arrow shown in figure 4 ) at the apex of the deformation element 20. The force symbolized by the arrow shown in figure 4 The force originates from the action of the weight of the container and the bulk material contained within it on the contact face of the force sensor housing, which is itself transmitted to the piston 22. The two strain gauges are fixed to the deformation element 20. Each strain gauge 24, 25 has at least one electrical characteristic that varies according to its deformation, the force sensor being arranged such that said electrical characteristic varies according to a deformation state of the deformation element 20. The deformation element 20 can take various forms different from that shown in figure 4 , for example the shape of a strip, a beam or a rod, or even a spiral. The deformation element 20 can be made of a metallic material (especially metal alloys), a ceramic material, a polymer material or a composite material.

[0063] The device also includes an electronic circuit: electrically connects to each strain gauge 24, 25 by cables 27, 28, adapted to measure said electrical characteristic of each strain gauge 24, 25, and to deliver a measurement signal, representative of said electrical characteristic of each strain gauge.

[0064] The strain gauges 24, 25 are resistive strain gauges, that is to say their resistance varies according to the deformation of the deformation part 20, which itself depends on the force exerted by the bottom of the container on the piston 22.

[0065] The second embodiment is shown in cross-section on the figure 5 This differs from the first embodiment in that it is a large, collapsible bulk container comprising a container in the form of a bag 33 made of flexible material, which contains inside a rigid container 30 that can be folded into a configuration with a smaller footprint than its normal operating configuration. The container containing the flexible bag 33 is placed on a pallet. The device includes a support 36 in the form of a pallet, allowing the device to be handled by a forklift.

[0066] The container has an opening 32 adapted to allow the introduction of a bulk material 35 into said container, the opening being disposed on the upper face, opposite the bottom 31 of the container.

[0067] The force sensor 1 is positioned in contact with the bottom of the flexible bag 33, both in contact with and outside of it. In the second embodiment shown in the figure 5 The force sensor 1 is positioned approximately in the center under the base 31 of the container. However, it can be placed elsewhere between the base of the container and the support 36, for example, closer to an edge of the container's flexible material bag 33. The results of measurements of the fill level of a large bulk container vary from one container to another (different geometries, material properties, etc.). A sensor placed under a large bulk container returns an electrical resistance value, which is converted into a strain value (principle of a strain gauge). For a large bulk container filled with 1000 L of water, for example, a strain of 0.055% of the strain element 20 is obtained, and a strain of 0.035% for 500 L of water.A law allows us to relate the volume (filling rate or percentage) to the deformation of the deformation element 20 of the force sensor 1. This law can be determined, in particular, from the first complete filling of the container from its initial empty state, the measured force variation then being considered as a variation from 0% to 100% filling. The flow rate of the bulk material introduced into the container during this first filling does not need to be constant but can vary, and the filling can be continuous or discontinuous (multiple fillings). It is not necessary to know the maximum capacity of the container, nor the density of the bulk material introduced into the container, but this data can, of course, also be used to refine the determined filling rate.During emptying, the evolution of the force detected by the force sensor and the comparison of any corresponding value with the first maximum value detected by the force sensor (associated with a 100% fill level) allows for the deduction (using a mathematical formula established based on specific parameters relating to the container and the nature of the bulk material) of a remaining volume or a fill level. This, for example, enables the system to trigger an alert when the fill level approaches zero or falls below 10%, 20%, or 30%. Despite some approximations, the inventors surprisingly found that this method achieves a result with an accuracy between 2% and 20%, for example, on the order of 10%. Such accuracy is more than sufficient and reliable for most applications and industries using such large bulk containers.

[0068] There figure 6 Figure 1 represents an example of how to display the result of measuring the container's fill level. The fill level is represented as an arc of a circle ranging from a minimum value of 42 (zero, or 0%) to a maximum value of 44 (100, or 100%). The actual value determined is 46 (100 in the example shown). figure 6 ) is positioned under the arc of the circle.

[0069] The invention is capable of numerous variations and applications other than those described above. In particular, it is understood that, unless otherwise specified, the various structural and functional features of each of the embodiments described above should not be considered as combined and / or closely and / or inextricably linked to one another, but rather as mere juxtapositions. Furthermore, the structural and / or functional features of the various embodiments described above may be juxtaposed or combined, in whole or in part, in any different manner. For example, containers with more complex shapes may be used.Furthermore, there is nothing preventing the use of other types of force sensors than strain gauge sensors, for example hydraulic, pneumatic, piezoelectric force sensors or even beam deflection sensors.

Claims

1. A device for storing at least one bulk material (35), said device comprising: - a container (10, 33) into which said bulk material selected from the group formed by liquids and powdered materials can be introduced, said container (10, 33) having a lower face forming a bottom (31) adapted to be able to be subjected to the weight of said bulk material introduced into said container, - a support (16, 36), separate from the container (10, 33) and from the bottom (31) of the container (10, 33), having an upper face (18) receiving the bottom of said container (10, 33), - a force measuring device comprising at least one force sensor (1) located outside said container (10, 33), disposed under the lower face forming the bottom (31) of the container (10, 30) and in contact with said lower face forming the bottom (31), wherein the storage device is arranged so that the lower face forming the bottom (31) of the container (10, 33) rests both on the force measuring device and on the support (16, 36), such that: - the container (10, 33) rests only partly on the force measuring device, - at least part of the bottom (31) of the container is supported in direct contact with the upper face (18) receiving the support (16, 36), - said upper face (18) receiving the support (16, 36) is adapted to be able to be subjected at least partly to the weight of said bulk material introduced into said container, and - said force measuring device is not subjected to the total weight of the bulk material introduced into said container, said storage device thus making it possible to determine the filling rate of said container (10, 33) and / or its variation without having to go through a measurement of the total weight of the bulk material (35) contained in said container (10, 33).

2. The device according to claim 1, characterized in that each force sensor (1) comprises at least one strain gauge.

3. The device according to any of claims 1 to 2, characterized in that each force sensor (1) comprises a casing incorporating two strain gauges (24, 25) and a strain element (20), the two strain gauges being fixed to said strain element.

4. The device according to claim 3, characterized in that each strain gauge (24, 25) has at least one electrical characteristic which varies as a function of its strain, each force sensor being arranged such that said electrical characteristic varies as a function of a strain state of said strain element (20).

5. The device according to claim 4, characterized in that it comprises an electronic circuit: - electrically connected to each strain gauge (24, 25), - adapted to measure said electrical characteristic of each strain gauge (24, 25), and to deliver a signal, called measurement signal, representative of said electrical characteristic of each strain gauge.

6. The device according to any of claims 1 to 5, characterized in that each force sensor (1) has a smaller dimension comprised between 1 mm and 15 mm.

7. The device according to any of claims 1 to 6, characterized in that each force sensor (1) has an upper face, called contact face, which is substantially planar, said contact face being adapted to be able to be in contact with said bottom (31) of the container (10, 33).

8. The device according to any of claims 1 to 7, characterized in that each force sensor (1) has a lower fixing face adapted to be able to allow the fixing of said force sensor on the upper face (18) receiving the support.

9. The device according to any of claims 1 to 8, characterized in that said force measuring device comprises a single force sensor (1).

10. The device according to any of claims 1 to 9, characterized in that said container (10, 33) has a maximum capacity comprised between 500 L and 1,200 L.

11. The device according to any of claims 1 to 10, characterized in that said container (10, 33) has a generally substantially cubic shape.

12. The device according to any of claims 1 to 11, characterized in that said container (10, 33) has an opening (12, 32) adapted to allow the introduction of said bulk material (35) inside said container.

13. The device according to any of claims 1 to 12, characterized in that said container (10, 33) has a bottom formed of at least one flexible material.

14. The device according to any of claims 1 to 13, characterized in that it comprises a wireless communication module.

15. The device according to any of claims 1 to 14, characterized in that it comprises an electric accumulator (4).