Dosing device and method for dosing product into packages

Abstract

Dosing device (1) for filling bags with a powder or granular product, said dosing device comprising: a supply hopper (21) containing a quantity of product, a dosing device (22) associated with said supply hopper (21) and configured to withdraw said product from said supply hopper (21) and to discharge doses of the withdrawn product into respective bags; a refill hopper (31) configured to store said product; a refill unit (32) configured to refill said supply hopper (21); a weighing unit (41) associated with said supply hopper (21) and configured to measure the weight of the supply hopper (21) and the product contained therein; and a controller (6) operatively associated with at least said refill unit (32) and said weighing unit (41), and programmed to operate said refill unit (32) to transfer the product from said refill hopper (31) to said supply hopper (21); wherein said controller (6) is further programmed to obtain by said weighing unit (41) an operation weight corresponding to a weight of a pre-established quantity of product inside the supply hopper (21) measured in a stationary condition, that is before starting discharging the doses of product into the bags, and to control a feed rate of said refill unit (32) to operate it in a condition to keep the weight measured by the weighing unit (41), when the doses of the product are discharged into the respective bags, at a value within ± 5% of the operation weight.

Description

[0001] "DOSING DEVICE AND METHOD FOR DOSING PRODUCT INTO PACKAGES"

[0002] SCOPE OF APPLICATION

[0003] The present invention refers to a dosing device for dosing a load of product into bags and a related method thereof. In particular, the dosing device is configured to dose a granular or powdered product in product packaging applications, such as food, pharmaceutical or infusion products.

[0004] STATE OF THE ART

[0005] In the field of packaging of granular or powdered products, such as pet food, in the coarse range, or ground tea and coffee for infusions, in the fine particle range, the use of a hopper with a small capacity is known. Such hopper is configured to receive certain quantities or batches of product from an upstream storage device or silo with a volumetric capacity far greater than the hopper. In addition, the hopper with small capacity is typically arranged upstream of a dosing element configured to dispense doses of product to be packaged.

[0006] While the upstream storage device or silo is dimensioned to contain significant quantities of product, for example sufficient for the needs of a packaging plant for an entire working day, the hopper with limited capacity allows a small, temporary storage upstream of the dosing element, sufficient to allow the dosing element to dispense doses of product to be packaged for a period lasting a few seconds up to a few minutes in the absence of a refill. In fact, the scope of the hopper with a small capacity is to act as a buffer between the upstream storage device or silo and the metering element, e.g. an augershaped screw, arranged downstream the hopper. As far as the reloading of the buffer hopper is concerned, it is known in the prior art that automation is used to detect the need to refill the same. In particular, it is known that a level sensor is used to continuously measure the fill level of the buffer hopper. The value detected by the level sensor is used to control the refilling of the buffer hopper before the quantity of product available inside it is exhausted, avoiding stopping the product packaging process.

[0007] Such a continuous level sensor may be of the ultrasonic transducer type, wherein a transducer, arranged above the hopper, emits an acoustic signal and detects the echo reflected from the surface of the granular or powdered product contained in that tank or hopper. The detected signal indicates the distance between the transducer and the interrogated surface.

[0008] Continuous level detection can be achieved alternatively through electromagnetic detection techniques, in particular with the use of a probe of the RADAR (RAdio Detection And Ranging) type. In such cases, the level sensor includes a transducer, arranged above the hopper, which emits electromagnetic waves in the microwave spectrum (in the range of Megahertz and Gigahertz) or millimeter waves (mmWave). Similarly, the echo signal is detected to measure the elapsed time of flight (ToF) between the emission of the electromagnetic wave and the detection of the echo of the same, to obtain the distance between the level sensor and the product surface, and consequently to estimate the fill level of the hopper.

[0009] It should be noted that, although these techniques offer the advantage of continuous operation compared to point level sensors, such solutions present a considerable economic cost compared to point level sensors that indicate the whether a threshold has been reached. In addition, the coarser the granular product to be packaged is, the more irregular the profile of the product surface inside the hopper can be, thus potentially leading to errors in detecting the actual filling of the hopper based on a volumetric basis.

[0010] It should be noted that buffer hoppers are typically equipped with agitator elements, which evenly distribute the product contained therein, preventing quantities of product from sticking to the walls of the buffer hopper or tank. Such agitator elements typically include an impeller connected to a shaft to rotate inside the hopper, consequently moving the product contained therein. In such cases, the construction details of the agitator element can be an additional disturbance to the use of continuous level sensors such as ultrasonic transducers or RADAR.

[0011] In addition, the use of continuous level sensors with sampling at a considerable frequency requires the digital processing of the detected signal. In particular, since these sensors calculate the distance between the probe and the detected obstacle, namely the product inside the hopper, it will be necessary to implement an additional calculation as a function of the measured distance, depending on the geometry of the buffer hopper to obtain more reliable measurements of the product level.

[0012] Therefore, there is a need to improve a dosing device and a related method for dosing a product within its packaging, which can overcome the drawbacks of the known art.

[0013] For achieving so, it is required to solve the technical problem of allowing finer control of the buffer hopper refill. In particular, one aim of the present invention is to provide a device and a respective method for dosing a product of the granular or powder type, in product packaging applications that is economically efficient.

[0014] Another aim of the present invention is to provide a device and a method for dosing a granular or powdered product, in product packaging applications that allows a precise measurement of the product inside the buffer hopper.

[0015] Another aim of the present invention is to provide a device and a method for dosing a product of the granular or powder type, in product packaging applications that is easy to implement.

[0016] Another aim of the present invention is to provide a device and a method for dosing a product of the granular or powder type, in product packaging applications that performs a direct measurement of the product present inside the buffer hopper and consequently does not require further calculations.

[0017] In order to overcome the drawbacks of the known technique and to obtain these and other aims and advantages, the applicant has studied, tested and implemented the invention.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention is expressed and characterized in the independent claims. Dependent claims expose other features of the present invention or variants of the present invention.

[0020] In accordance with the aforementioned purposes and in order to solve the aforementioned technical problem in a new and original way, also obtaining considerable advantages compared to the previous state of technology, according to the invention a dosing device is provided for filling bags with a powder or granular product, wherein the device comprises a supply hopper containing a quantity of product, a dosing device associated with the supply hopper and configured to withdraw the product from the supply hopper and to discharge doses of the withdrawn product into respective bags, a refill hopper configured to store quantities of product, a refill unit configured to refill said supply hopper, a weighing unit associated with the supply hopper and configured to measure the weight of the supply hopper and the quantity of product contained therein, and a controller operatively associated with at least the refill unit and the weighing unit, and programmed to operate the refill unit to transfer the product from the refill hopper to the supply hopper.

[0021] Preferably, the supply hopper comprises an upper opening, which will be appropriately configured to associate with the dosing device so that the supply hopper accommodates the product coming from the refill hopper.

[0022] In accordance with one aspect of the invention, the controller is further programmed to obtain by the weighing unit an operation weight corresponding to a weight of a pre-established quantity of product contained inside the supply hopper measured in a stationary condition, that is before the product is discharged from the supply hopper, and to control a feed rate of said refill unit to operate it in a condition to keep the weight measured by the weighing unit, when the doses of the product are discharged into the respective bags, at a value within ± 5% of the operation weight.

[0023] In other worlds, after the supply hopper has been filled with pre-established quantity of product, the weight of the supply hopper and of the pre-established quantity of product is measured in a stationary condition and taken as operation weight.

[0024] Preferably, the weighing unit consists of a load cell. Preferably, the load cell is of the type chosen between a strain gauge load cell and a capacitive load cell.

[0025] Preferably, the device is configured to record the tare weight of the elements resting on the weighing unit, starting from the supply hopper, and, using it, allows you to calculate the quantity of product present in the dosing device.

[0026] Such implementation results in having an instant measurement of the weight of the product inside the supply hopper through the weighing unit. This piece of information is used by the controller to operate the refill unit and ensure an optimal filling of the supply hopper, allowing a stable and continuous operation of the dosing device used for packaging products.

[0027] In accordance with another aspect of the present invention, the device may include an agitator arranged inside the supply hopper for stirring the product contained therein.

[0028] Preferably, the agitator includes an impeller.

[0029] Preferably the impeller is connected to a shaft.

[0030] In this way, the device can effectively monitor the weight of the weighing unit, as it is placed outside the supply hopper, so that the agitator will not interfere with the operation of the weighing unit in any way.

[0031] According to another aspect of the present invention, the device comprises a base assembly on which the weighing unit is fixed and wherein the supply hopper is mounted on a translation body contacting the weighing unit and slidingly mounted on the base assembly.

[0032] Preferably, the device translation body is arranged vertically so as to handle the supply hopper in the vertical direction. Preferably, the translation body comprises a fastener to support at least the supply hopper.

[0033] Advantageously, the translation body can also include a linear actuator configured for the vertical stroke of the translation body. Advantageously, the linear actuator will be connected to the controller for its automatic actuation. In doing so, the device can give flexibility of operation to work in a plurality of vertical positions, allowing in any case to burden the weighing unit to obtain an accurate measurement.

[0034] According to another aspect of the present invention, the translation body comprises sliding guide bars slidingly mounted within a sliding profile fixed to the base assembly.

[0035] This way, the sliding guide bars constrain the movement of the dosing device in the vertical direction, giving stability during the operation of the same in case the operating height is changed.

[0036] Preferably, the base assembly comprises fixed sliding carriages for sliding the guide bars of the translation body. In this way, the translation body will slide stably on the fixed base assembly.

[0037] The embodiments wherein the linear actuator is comprised in the translation body provide that the linear actuator is fixed to the weighing unit. By doing so, the supply hopper will weigh directly on the weighing unit, ensuring the effectiveness of the weighing.

[0038] In accordance with a particularly advantageous aspect of the present invention, the dosing device comprises a rotating auger having a vertical rotating axis, wherein a portion of the rotating auger is arranged within the supply hopper. This way, the auger can remove quantities of product from the supply hopper to be packed in bags, which are arranged downstream of the dosing device.

[0039] In accordance with a particularly advantageous aspect of the present invention, the refill unit comprises a rotating screw for continuously transferring the product into the supply hopper.

[0040] Preferably, the rotating screw is driven by a dedicated electric motor. Preferably, the motor is connected to the controller.

[0041] Accordingly, an effective and precise refill of product in the supply hopper is obtained, thus resulting in an instantaneous buffer in a small supply hopper upstream of the dosing device.

[0042] In accordance with a particularly advantageous aspect of the invention, the rotating screw of the refill unit lies substantially horizontally. Such rotating screw provides for continuative refilling of the hopper, wherein the product stream can be modulated by tuning the speed of the rotating screw. In accordance with a particularly advantageous aspect of the present invention, the refill hopper and the supply hopper are connected through an elastic duct interposed in between for the transfer of the product from the refill hopper to the supply hopper. Thus, product losses due to the transfer from the first to the latter hopper will be minimized, if not avoided.

[0043] Preferably, the controller is configured to additionally store a maximum threshold value of supply-hopper weight.

[0044] By doing so, a maximum value related to the maximum capacity of the supply hopper is defined, so as not to overfill it, avoiding undesirable effects of clogging the same or causing product overflowing from the hopper due to excessive refilling. In addition to the supply hopper tare, which is a theoretical minimum threshold, having the maximum weight threshold will allow to set up a more accurate supply hopper refill strategy. For example, it will be possible to set the refill to restart whenever the weighing unit determines a product weight of less than 90% of the maximum load that can be contained inside the supply hopper.

[0045] According to a particularly advantageous design form of the present invention, the device further comprises a level probe configured to measure the level of the quantity of product within the supply hopper, wherein the controller is further programmed to associate the weight detected by the weighing unit to corresponding levels measured by the level probe.

[0046] Preferably, the level probe is of the point-level type and is arranged in the top part of the supply hopper. This arrangement makes possible to determine the maximum weight threshold in a convenient manner, enabling an initial calibration of the supply hopper capacity, before starting the continuative refill of product to be packaged in the supply hopper. This aspect is particularly advantageous when the density of the product to be dosed is not known in advance.

[0047] Preferably, the point level probe is arranged on top of the supply hopper. This configuration enhances the effective capacity of the supply hopper.

[0048] Preferably, the point level probe is of the capacitive type. The capacitive- type level probe is particularly advantageous because it is a cost-effective technology and compatible with a wide range of granular and / or powder products. According to a particularly advantageous embodiment of the present invention, the pre-established quantity of product inside the supply hopper corresponds to a quantity of product which reaches a pre-established height within the supply hopper.

[0049] Alternatively, the level prove is of the continuous type, and is arranged pointing towards the inner walls of the hopper. Provided that the geometry of the hopper is known, this alternative provides for a calibration of the product density without totally filling the supply hopper with product.

[0050] Preferably, the controller is further programmed to store geometric information of the supply hopper, to calculate the density of the product, and to calculate, starting from this calculated density of product, from the geometric information of the supply hopper and from an operating height chosen by an operator, the weight of the predetermined quantity of product with which the controller will control the drive of the charging element from the weight measured by the weighing unit.

[0051] Geometric information refers to the internal volume of the supply hopper and / or the geometric shape of the supply hopper as a function of the filling height (i.e.: in the vertical direction), thus enabling the calculation of the product density, and the product quantity (weight) from a predefined filling height.

[0052] As far as the product density is concerned, it is defined as the quotient of the division between the weight of product, measured by the weighing unit, and the internal volume of the supply hopper. The weight reading will be contextual to the detection of the filling of the internal volume by the level probe. The calculation of the weight starting from a height of the supply hopper will be calculated, starting from the bottom of the supply hopper, making the integral of the differential or the summation of the incremental volumes as a function of this height up to the desired height multiplied by the calculated product density.

[0053] The calculation of weight as a function of the height is particularly advantageous in this type of device, as operators are used to choose a supply hopper filling height instead of weight as the operating setpoint in state-of-the- art solutions. Such parameter is basically associated with solutions including a continuous level probe as an alternative to the supply hopper weighing unit of the present invention.

[0054] The invention extends its scope of protection to a method for packaging powder or granular-type products in individual bags.

[0055] The method for packaging powder or granular-type products comprises the steps of: a. providing a supply hopper containing a product; b. withdrawing the product from the supply hopper and discharging doses of the withdrawn product into respective bags; c. providing a refill hopper for storing said product; d. refilling the supply hopper operating a refill unit to transfer the product from the refill hopper to the supply hopper; and e. measuring the weight of the supply hopper and of the product contained therein by means of a weighing unit associated to the hopper. In accordance with one aspect of the invention, the method further comprises a step of setting an operation weight corresponding to a weight of a pre-established quantity of product contained inside the supply hopper measured by the weighing unit in a stationary condition, that is before starting the step of discharging the doses of product. In particular, the step of refilling the supply hopper comprises operating the refill unit at a feed rate suitable for keeping the weight measured by the weighing unit, during the step of discharging the doses of the product, at a value within ± 5% of the operation weight.

[0056] Keeping a predetermined quantity of product inside the supply hopper allows a continuous and effective operation in order to ensure high productivity in packaging plants for granular or powdered products.

[0057] In accordance with an aspect of the invention, the method further comprises, before the step of discharging the doses of product, a step of determining the density of the product according to the volume and the operation weight of the pre-established quantity of product contained in the supply hopper, wherein the volume of the pre-established quantity of product is determined by taking into account a level of the product within the supply hopper, preferably measured by a level probe.

[0058] The determination of the supply hopper capacity optimizes the calculations of the thresholds within which to control the start and stop of the supply hopper refill, first of all, avoiding filling the supply hopper until it overflows or gets clogged.

[0059] In accordance with an aspect of the invention, the step of refilling is carried out by means of a rotating screw of the refill unit, which continuously refills the product into the supply hopper. In accordance with an aspect of the invention, the step of discharging is carried out by means of a rotating auger having a vertical rotating axis, wherein a portion of the rotating auger is arranged within the supply hopper.

[0060] In accordance with an aspect of the invention, the pre-established quantity of product inside the supply hopper corresponds to a quantity of product which reaches a pre-established height within the supply hopper.

[0061] The level probe suitably arranged in correspondence with the maximum filling level will allow the automatic determination of the supply hopper capacity, not requiring manual procedures both for the progressive loading of the supply hopper and for recording the capacity value. Preferably, a level probe of the capacitive type will be used, which allows for precise detection of a threshold level and is economical.

[0062] Advantageously, establishing a predetermined upper weight threshold to stop the refilling step helps to avoid clogging the supply hopper due to overfilling of the supply hopper or possible overflow once the maximum capacity has been exceeded. As mentioned before, it is possible to determine with a level probe the maximum capacity in terms of weight of the product inside the supply hopper. Alternatively, it is possible to use pre-existing information related to a given product. It will be possible, for example, to establish a threshold of 90% of the maximum capacity of the supply hopper as an upper threshold beyond which recharging will be stopped.

[0063] Advantageously, it will be possible to establish the product weight threshold according to the height of the product present in the supply hopper. In such embodiments, the method involves calculating first of all the density of the product by dividing the weight of the product contained inside by the internal volume of the supply hopper. Starting from such density and the well-known internal geometry of the supply hopper, the threshold weight can be calculated from a predefined filling height. In such embodiments, the method will calculate the weight threshold from the density of the product obtained and a preset threshold height. Advantageously, an operator will be able to choose the threshold height in a human-machine interface, such as a graphical user interface (GUI). Starting from this threshold height, the method provides for the calculation of the equivalent weight with which to activate the recharge step.

[0064] DESCRIPTION OF THE DRAWINGS

[0065] These and other aspects, characteristics and advantages of the present invention will be clear from the following description of particular embodiments thereof, provided by way of example, but not limited to, with reference to the attached drawings wherein:

[0066] - Fig. 1 is a general axonometric view of a dosing device according to the present finding;

[0067] - Fig. 2 is an axonometric detail view of a dosing device, with particular reference to a supply hopper and a weighing unit, according to the present invention;

[0068] - Fig. 3 is an axonometric view of a base assembly of the dosing device according to the present invention;

[0069] - Fig. 4 is an axonometric view of a translation body of a dosing device according to the present finding;

[0070] Fig. 5 is an axonometric view of a screw dosing unit of a dosing device according to the present invention;

[0071] Figs. 6a, 6b, 6c, 6d and 6e schematically represent the operation of the dosing device.

[0072] It should be noted that in this description the phraseology and terminology used, as well as the figures of the attached drawings, also as described, have the sole function of illustrating and explaining better the present invention, having a non-limiting exemplary function of the invention itself, being the scope of protection defined by the claims.

[0073] To facilitate understanding, identical reference numbers have been used, where possible, to identify identical common elements in the figures. It should be understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarification.

[0074] DESCRIPTION OF THE EMBODIMENTS OF THE PRESENT INVENTION

[0075] With reference to figure 1 , a dosing device 1 according to the invention is configured to dose a product into packages. The dosing device 1 comprises a supply hopper 21 , a dosing device 22, a storage device 31 , a product refill unit 32, a weighing unit 41 and a controller 6.

[0076] The supply hopper 21 is configured and sized to receive the product. In addition, the dosing device 22 is associated with the supply hopper 21. The dosing device 22 is configured to remove doses of product from the supply hopper 21 .

[0077] According to an embodiment, the supply hopper 21 and the dosing device 22 can be associated with a screw dosing unit 2.

[0078] The dosing device 22 is operated by driving means 23 of the dosing device 22. The driving means 23 of the dosing device 22 may comprise a first electric motor 231 . The dosing device 22 is configured to convey doses of product in a forming unit 7. The forming unit 7 is configured to wrap a film around itself and create a tubular wrapper by longitudinally sealing the longitudinal ends of the film for the insertion of doses of product inside the tubular wrapper. In addition, the forming unit 7 normally comprises a transversal sealing and cutting device to close and separate these tubular casings creating packages 10 already filled with the product.

[0079] The refill hopper 31 is configured to store the product to be packaged. In addition, the refill unit 32 is configured to refill the supply hopper 21 with product.

[0080] The refill hopper 31 and the refill unit 32 can be associated with a pre-dosing unit 3. The refill unit 32 comprises a rotating screw 321 for conveying the product to the supply hopper 21 . The rotating screw 321 may lie substantially horizontally.

[0081] The refill unit 32 is operated by handling means 33 of the refill unit 32. Accordingly, the driving means 33 of the refill unit 32 comprise a second electric motor 331 .The weighing unit 41 is configured to measure the weight of the supply hopper 21 and the quantity of product contained therein. Preferably, the weighing unit 41 is a load cell 41. The load cell 41 may be of the strain gauge type; alternatively, it can be of the capacitive type.

[0082] The supply hopper 21 is fixed to a fastening element 51 on the weighing unit 41 , so that the weighing unit 41 detects the weight of the supply hopper 21 and the product contained therein.

[0083] In particular, the weighing unit 41 is configured to measure the weight of the supply hopper 21 containing the product. Starting from the tare weight of the empty supply hopper 21 , the quantity of product contained inside can be calculated. In other words, the weight of the registered empty supply hopper 21 can be subtracted from the total weight of supply hopper 21 containing product to determine the amount of granular or powdered product inside it.

[0084] A controller 6 is paired with at least the refill unit 32 and with the weighing unit 41. In particular, the controller 6 is associated to the weighing unit 41 , in particular to the load cell 41. The controller 6 is programmed to operate the refill unit 32 in order to dispense product to maintain a predetermined quantity of product within the supply hopper 21 according to the signal received from the weighing unit 41 . In particular, the controller 6 is configured to operate the refill unit 32 based on the weight detected by the weighing unit 41 .

[0085] The dosing device 1 may include an agitator 24. The agitator 24 is arranged inside the supply hopper 21 for handling the product contained therein.

[0086] The agitator 24 is driven by a third electric motor 241 . The agitator 24 comprises a shaft 242 connected to the third motor 241 , and an impeller 243. The 243 impeller is preferably sized to fit the shape of the supply hopper 21 . In this way, the impeller 243 of the agitator 24 will be able to operate close to the walls of the supply hopper 21 , preventing the granular product, particularly when the product is of the fine-powder type, from sticking to the walls. In addition, the operation of the agitator 24 will ensure that the product is recirculated and conveyed to the screw dosing unit 2.

[0087] With reference to figure 3, the dosing device 1 comprises a fixed base assembly 4. The weighing unit 41 is comprised in the base assembly 4. Typically, the weighing unit 41 can be attached to the base assembly 4. For example, the weighing unit 41 can be attached to a connecting element 42 of the base assembly 4. In this way, the weight signal detected by the weighing unit 41 will be more accurate as it is not subject to movement dynamics. The base assembly 4 comprises sliding carnages 43, preferably a couple of carnages 43, wherein respective guides slide. The sliding carriages 43 are preferably oriented in the vertical direction, so that the guides can slide in such direction. The sliding carnages 43 are reciprocally arranged at a predetermined distance in two parallel rows.

[0088] With reference to figure 4, the dosing device 1 comprises a translation body 5. The translation body 5 comprises a plate 51 for fixing the screw dosing unit 2. In addition, the translation body 5 comprises sliding guiding bars 52. The sliding guide bars 52 are mounted on the plate 51. Preferably, there are two sliding guide bars 52, which are arranged parallel to each other at a predetermined distance. The distance between the two guide bars 52 will be such as to allow sliding in the carriages 43 of the base assembly 4. This allows the translation body 5 to slide in the vertical direction over the base assembly 4.

[0089] The translation body 5 further comprises a gantry structure 53 mounted on the fixing plate 51 on the opposite side with respect to where the two guide bars 52 have been attached. This gantry structure 53 comprises two vertically oriented 531 support elements and a horizontally arranged 532 connecting element. The connecting element 532 and the fixing plate 51 are arranged perpendicularly to each other, allowing their assembly to a supporting structure of the supply hopper 21 on top of the gantry structure 53.

[0090] The translation body 5 further comprises a linear actuator 54. The linear actuator 54 is arranged in a vertical direction. The linear actuator 54 is fixed from a first end 541 to the base assembly 4. In particular, the first end of the linear actuator 54 is attached to the connecting element 42 of the base assembly 4. With this configuration, translation body 5 will burden on the weighing unit 41 . On the other hand, the linear actuator 54 is attached to the second end to the connecting element 532. In this way, the drive of the linear actuator 54 will allow the controlled vertical translation of the translation body 5 with respect to the base assembly 4.

[0091] The first electric motor 231 and / or second electric motor 331 and / or the third electric motor 241 and / or the linear actuator 54 can be connected to the controller 6.

[0092] With reference to figure 5, the screw dosing unit 2 includes the supply hopper 21 , the dosing device 22 and an upper opening 25. The supply hopper 21 preferably has a truncated cone shape, so that agitator 24 can operate near a side wall 211 of supply hopper 21 by rotating the impeller 243. In addition, the supply hopper may comprise an upper wall 212.

[0093] The screw dosing unit 2 further comprises a connecting element 2121 for connecting a support beam 28 of supply hopper 21 to the translation body 5, in particular to the connecting element 532. The connecting element 2121 is mounted on the upper wall 212 of the supply hopper 21 . The support beam 28 is fixed above the connecting element 2121. Accordingly, the screw dosing unit 2 will be connected to the translation body 5. As a result, the screw dosing unit 2 and the translation body 5 will burden on the weighing unit 41. This configuration enables the weighing of the product contained in the supply hopper 21 once the tare weight of the empty screw dosing unit 2 and the translation body 5 have been made.

[0094] The support beam 28 is also configured to accommodate the driving means

[0095] 23 of the dosing device 22. The support beam 28 further comprises a seat to accommodate the third motor 241 for the movement of the agitator 24. The upper wall 212 comprises an upper opening 25 for the transfer of product from the pre-dosing unit 3 to the supply hopper 21. This opening 25 can be obtained directly on the upper wall 212. Alternatively, the opening 25 may have the shape of an upper protrusion 251 , for example with a cylindrical shape, for connecting the supply hopper 21 through a connection duct 34. The connecting duct 34 may be partially elastic. The upper protrusion 251 of the opening has the advantage of being able to accommodate a point level probe 252. The point level probe 252, when the threshold is reached, emits a corresponding signal. Typically, the point level probe 252 is of the capacitive type.

[0096] The point level probe 252, in combination with the weight reading of the weighing unit 41 , allows the controller 6 to determine the capacity of the supply hopper 21 for a given product, and consequently establishing the thresholds for activating or stopping the recharging of the device.

[0097] In addition, the controller 6 can be configured to store the volumetric capacity and / or geometry of the supply hopper 21 , and / or the density of the product to be monitored. This is particularly advantageous because it allows the weight of the product contained in supply hopper 21 to be associated with the product level detected.

[0098] The controller 6 uses the weight detected by the weighing unit 41 when the point level probe 252 detects that supply hopper 21 is full to calculate the actual density of the product. The controller 6 will then use the geometric information of the supply hopper 21 to associate a setpoint fill height with a corresponding supply hopper fill weight.

[0099] In this way, the operator in charge of the production system will be able to choose the filling level of the supply hopper 21 as a function of the height in a dedicated Graphical User Interface (GUI), while the refill system will continue to use the value detected by the weighing unit 41 as an operating parameter of the dosing device 1 to control the refill unit 32.

[0100] The screw dosing unit 2 further comprises a relief valve 26 for the discharge of overpressures. The relief valve 26 may be arranged on the upper wall 212 of the supply hopper.

[0101] With reference to figures 6a, 6b, 6c, 6D and 6e a method for operating the dosing device 1 is shown.

[0102] In fact, the method involves, before the step of removing predetermined quantities of product by means of the dosing device 22, a step of determining the capacity of the supply hopper 21 by measuring the weight of the pre- established quantity of product contained inside the same upon its fulfillment.

[0103] Figure 6a shows that an interface 8 is connected to the controller 6 of the forming device. In an initial condition, the supply hopper 21 may be substantially empty, as a result the weighing unit 41 detects a weight of zero and the point level probe 252 will detect an unfilled state.

[0104] Figure 6b shows a subsequent step when the supply hopper 21 is full with the pre-established quantity of product. The achievement of the maximum filling is detected by the capacitive point level probe 252. At the same time, weighing unit 41 detects the weight of the pre-established quantity of product contained inside the supply hopper. Controller 6 records the weight measurement detected by the weighing unit 41 when the volume is fulfilled and, starting from the geometric information of the hopper stored in the controller 6, calculates the density p of the product. In particular, the geometric information stored includes the volume used for filling the product. Advantageously, the method provides that the step of refilling is activated according to a percentage of the capacity of the supply hopper 21 . In particular, this embodiment requires an operator to choose an operating height hsetpoint in a dedicated interface 8 of the dosing device. The hsetpoint operating height is measured from the bottom of the supply hopper 21 .

[0105] Figure 6c shows a step of selection of the hsetpoint operating height. The operator selects an operating height value hsetpoint with respect to the bottom of the supply hopper 21 in the graphical interface 8.

[0106] Figure 6d shows a further step in the setting of the dosing device 1 based on the preset operating height (degree of filling). In particular, Fig. 6d shows the calculation of the equivalent weight W from the product density p calculated by the controller s. Thanks to the geometric information stored in the controller 6, it will be possible to calculate the equivalent weight of the volume occupied by the product until the controlled operating height hsetpoint is reached. In particular, the geometric information stored will be the transverse area A of the supply hopper as a function of the height of the same. In practice, for each height increment A / ? / , the controller 6 stores a respective transverse area Ai. The equivalent weight W delivery setpoint is equal to the sum of the product of the N incremental heights for the respective incremental areas until the selected hsetpoint operating height is reached and multiplied by the product density p previously calculated by controller 6.

[0107] Finally, figure 6e shows the operation of the dosing device 1 at full speed. In practice, the controller 6 commands the operation of the refill unit 32 when the weighing unit 41 detects a weight W below the equivalent weight \Nsetpoint corresponding to the operating height hsetpoint selected by the operator. Alternative embodiments of the invention provide for the use of a continuous level probe 27. The continuous level probe 27 will be placed on the upper wall 212 of the supply hopper and oriented downwards. The continuous level probe 27 is configured to continuously measure with respect to the product level inside the supply hopper 21 . The continuous level probe 27 uses time-of-flight measurement (ToF) techniques. The continuous level probe 27 can be of the ultrasonic or RADAR type or use other techniques based on the ToF principle. Starting from the measurement of the distance between the probe 27 and the product level, the calculation of the filling degree of the supply hopper 21 will be carried out.

[0108] As mentioned before, since the operator will choose a filling height of the hopper 21 in the GUI, the use of the continuous level probe 27 will allow to have an alternative source of information to the weight detected by the weighing unit 41 about the degree of filling of the supply hopper 21 .

[0109] This is because the continuous level probe 27 operates in parallel with the weighing unit 41. In such cases, the controller 6 will be configured and programmed to choose between the measurements of one of the two measured values depending on the product to be dosed, and / or to combine both values detected by the continuous level probe 27 and the weighing unit 41.

Claims

CLAIMS1. Dosing device (1 ) for filling bags with a powder or granular product, said dosing device comprising:- a supply hopper (21 ) containing a quantity of product,- a dosing device (22) associated with said supply hopper (21 ) and configured to withdraw said product from said supply hopper (21 ) and to discharge doses of the withdrawn product into respective bags;- a refill hopper (31 ) configured to store said product;- a refill unit (32) configured to refill said supply hopper (21 );- a weighing unit (41 ) associated with said supply hopper (21 ) and configured to measure the weight of the supply hopper (21 ) and the product contained therein;- a controller (6) operatively associated with at least said refill unit (32) and said weighing unit (41 ), and programmed to operate said refill unit (32) to transfer the product from said refill hopper (31 ) to said supply hopper (21 ); characterized in that said controller (6) is further programmed to obtain by said weighing unit (41 ) an operation weight corresponding to a weight of a pre-established quantity of product contained inside the supply hopper (21 ) measured in a stationary condition, that is before starting discharging the doses of product into the bags, and to control a feed rate of said refill unit (32) to operate it in a condition to keep the weight measured by the weighing unit (41 ), when the doses of the product are discharged into the respective bags, at a value within ± 5% of the operation weight.

2. The device as in the previous claim, characterized by further comprising an agitator (24) arranged inside said supply hopper (21 ) for stirring the product contained therein.

3. The device as in claim 1 or 2, characterized by further comprising a base assembly (4) on which the weighing unit (41 ) is fixed, said supply hopper (21 ) being mounted on a translation body (5) contacting the weighing unit (41 ) and slidingly mounted on said base assembly (4).

4. The device as in claim 3, characterized in that said translation body (5) comprises guide bars (52) slidingly mounted within a sliding profile (43) fixed to the base assembly (4).

5. The device as in any one of the previous claims, characterized in that said dosing device (22) comprises a rotating auger (22) having a vertical rotating axis, and in that a portion of said rotating auger (22) is arranged within said supply hopper (21 ).

6. The device as in any one of the previous claims, characterized in that said refill unit (32) comprises a rotating screw (321 ) for continuously transfer the product into said hopper (21 ).

7. The device as in claim 6, characterized in that said rotating screw (321 ) lies substantially horizontally.

8. The device as in any one of the previous claims, characterized in that said refill hopper (31 ) and said supply hopper (21 ) are connected through an elastic duct (34) interposed in between for the transfer of the product from the refill hopper (31 ) to the supply hopper (21 ).

9. The device as in any of the previous claim, characterized by further comprising a level probe (252, 27) configured to measure the level of theproduct within the supply hopper (21 ) and in that said controller (6) is further programmed to associate the weight detected by the weighing unit (41 ) to corresponding levels measured by said level probe (252, 27).

10. The device as in any of the previous claim, characterized in that said pre- established quantity of product inside the supply hopper (21 ) correspond to a quantity of product which reaches a pre-established height (hsetpoint) within the supply hopper (21 ).11 . Method for packaging a powder or granular product in individual bags, said method comprising the steps of: a. providing a supply hopper (21 ) containing a product; b. withdrawing said product from said supply hopper (21 ) and discharging doses of the withdrawn product into respective bags; c. providing a refill hopper (31 ) for storing said product; d. refilling said supply hopper (21 ) operating a refill unit (32) to transfer the product from said refill hopper (31 ) to said supply hopper (21 ); e. measuring the weight of the supply hopper (21 ) and of the product contained therein by means of a weighing unit (41 ) associated to said hopper (21 ), characterized by further comprising a step of setting an operation weight corresponding to a weight of a pre-established quantity of product contained inside the supply hopper (21 ) measured by said weighing unit (41 ) in a stationary condition, that is before starting the step of discharging the doses of product, and in that the step of refilling said supply hopper (21 ) comprises operating the refill unit (32) at a feed rate suitable forkeeping the weight measured by the weighing unit (41 ), during the step of discharging the doses of the product, at a value within ± 5% of the operation weight.

12. The method as in the previous claim, characterized by comprising, before the step of discharging the doses of product, a step of determining the density of the product according to the volume and the operation weight of said pre-established quantity of product contained in said supply hopper (21 ), said volume of said pre-established quantity of product being determined taking into account a level of the product within the supply hopper (21 ), preferably measured by a level probe (252, 27).

13. The method as in claim 11 or 12, characterized in that the step of refilling is carried out by means of a rotating screw (321 ) of said refill unit (32) which continuously refills the product into said supply hopper (21 ).

14. The method as in any claim 11 -13, characterized in that the step of discharging is carried out by means of a rotating auger (22) having a vertical rotating axis, wherein a portion of said rotating auger (22) is arranged within said supply hopper (21 ).

15. The method as in any claim 11 - 14, characterized in that said pre- established quantity of product inside the supply hopper (21 ) corresponds to a quantity of product which reaches a pre-established height (hsetpoint) within the supply hopper (21 ).

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