WO2008139295A2

WO2008139295A2 - System and corresponding method for weighing a product, dosed by a filling machine, in elements, in particular capsules and the like

Info

Publication number: WO2008139295A2
Application number: PCT/IB2008/001131
Authority: WO
Inventors: Roberto Trebbi
Original assignee: I.M.A. Industria Macchine Automatiche S.P.A.
Priority date: 2007-05-09
Filing date: 2008-05-08
Publication date: 2008-11-20
Also published as: ITBO20070336A1; WO2008139295A3

Abstract

A system, and corresponding method, for weighing a product dosed in elements (100), in particular capsules of hard gelatine, by a filling machine (3), comprises a weighing apparatus (2), first movement means (4) for transferring empty elements (100) from the said weighing apparatus (2) to the filling machine (3) and second movement means (5) for transferring filled elements (100' ) with said dosed product from said filling machine (3) to said weighing apparatus (2); the weighing apparatus (2) comprises a weighing unit (20) for weighing each empty element (100) and each filled element (100'), processing means (10) connected to said weighing unit (20) for receiving data relating to weights measured by the latter and calculating for each element (100' ) a difference of weight measured before and after filling so as to determine a respective quantity of actually dosed product.

Description

System and. corresponding method for weighing a product, dosed by a filling machine, in elements, in particular capsules and the like.

The present invention relates to a system and a method for weighing elements, in particular for weighing small containers, such as capsules, filled by an automatic filling machine with pharmaceutical products .

In the processes of filling capsules of hard gelatine of the cover-base type, with pharmaceutical products in liquid, in powder, or granule form or in the form of tablets, it is known to use weighing apparatuses or devices that are placed downstream of the filling machine, outside the machine, to measure the weight of the product dosed inside said capsules. Checking weight is necessary both in order to reject capsules that do not conform because they contain a quantity of product outside the permitted dosage tolerance range and in order to correct possible excesses or defects in dosing the product, for example by using feedback on a filling group of the machine . Above all, in the pharmaceutical field, it is very important to check that the weight of product introduced into the single capsules is exactly what is required, with very narrow tolerance ranges . Generally, only one weighing of the capsules takes place at the end of dosing, as the weight of the empty capsules is known and falls within a preset tolerance range indicated and ensured by the suppliers/manufacturers of the capsules . In this manner, by measuring the weight of the filled capsule (gross weight) by subtracting the known weight of the empty capsule (tare weight) , it is possible to calculate the weight of the dosed product (net weight) with a certain degree of precision.

The weighing apparatuses that perform this type of direct measurement comprise electronic balances, typically load cells on which the capsules have to be positioned for a suitable time. There further exist apparatuses that enable the weight of the capsules to be measured indirectly, for example by measuring other sizes or physical parameters of the latter by means of suitable sensors (capacitive, magnetic, microwave, ...) . Regardless of the direct or indirect type of measuring, the weight control can be partial, statistic or be made on a sample of filled capsules chosen at random, or can be total, being conducted on all the filled capsules exiting the filling machine (100% control) . In the filling processes in which the quantity of product to be dosed inside each capsule is very small, for example only a few milligrams, and the tolerance range required for product dosing is narrow, for example ±10%, it is clear that the normal variations in the weight of the empty capsules, greatly affect and influence the measurement of the weight. In fact, as the weight of the empty capsules is comparable with that of the dosed product, these weight variations can be wider than the tolerance range of the required dosage . In this case, checking only the weight of the filled capsule is not sufficient to ensure that the quantity of dosed product is within the required limits and it is necessary to weigh the empty capsule beforehand and calculate of the weight of the dosed product by measuring the difference. Weighing systems are known that comprise a first weighing unit or balance, upstream of the machine or of the filling group, which measures the weight of the empty capsules (tare weight) , and a second weighing unit, downstream of the filling machine, which measures the weight of the filled capsules (gross weight) . The difference between the two measured weights enables the net weight of the dosed product to be calculated with precision.

Such systems have the drawback of permitting only a statistical check of the weight of the capsules, i.e. performed on a small sample thereof, as a total check of all the capsules would cause a very low and unsatisfactory production speed. In fact, for a correct measurement between the placing of the capsule on the balance and the measurement of the weight a minimum preset interval of time must elapse that is necessary for enabling the. vibrations to be damped that are generated by resting the capsule on the balance. In addition to that, such weighing systems have the further drawback of requiring two different and separate weighing units that weigh the same capsule before and after filling. Although such units are virtually identical they may deviate more or less noticeably from the measurements due to the variations in internal calibration arising during operation or due to various environmental factors (temperature, pressure, humidity, vibrations, electrostatic charges, electromagnetic waves, etc) to which said units are subject, also because they are positioned at different points of the machine or of the filling plant. Such measuring differences have a percentage effect that may also be significant if the weights to be measured are very small and so measurements with great accuracy and precision values are required. An object of the present invention is to improve known systems and methods for weighing elements, such as capsules, or similar small containers, filled with a product, in particular for pharmaceutical use, by an automatic filling machine . Another object is to provide a system and a method for checking the weight of all the elements, before and after filling, so as to determine in a precise and accurate manner the real effective weight of the dosed product in each element . A further object is to provide a system and a method for checking the weight of the elements, before and after filling, by means of the same weighing unit.

Still another object is to obtain a system and a method, and a corresponding plant that enables operations to be conducted at high speed. In a first aspect of the invention there is provided a system for weighing a product dosed in elements, in particular capsules of gelatine, by a filling machine, comprising a weighing apparatus, first movement means for transferring empty elements from said weighing apparatus to said filling machine and second movement means for transferring filled elements with said dosed product from said filling machine to said weighing apparatus, said weighing apparatus comprising a weighing unit for weighing each empty element and each filled element, processing means connected to said weighing unit for receiving data relating to weights measured by the latter and calculating for each element a weight difference measured before and after filling so as to determine a respective quantity of actually dosed product.

In a second aspect of the invention there is provided a method for weighing a dosed product in elements, in particular capsules of gelatine, by a filling machine, comprising weighing empty elements to be dosed by a weighing unit, transferring said empty weighed elements to said filling machine, transferring filled elements from said filling machine to said a weighing unit, weighing said filled elements by said weighing unit, calculating for each- filled element a weight difference measured before and after filling by said weighing unit so as to determine a respective quantity of actually dosed product. Owing to these aspects of the invention it is possible to obtain a system and a method for running a total or so-called 100% weight check of filled elements with a product dosed by a filling machine associated with the system to form a filling plant. In particular, the system weighs all the elements, before and after filling, measuring for each container the weight thereof when empty (weight tare) and the weight thereof when filled (gross weight) and then calculating the difference of the weight (net) of the product contained in said element. In this manner, possible weight variations of the different empty elements cannot influence the final measurement.

The system and the method of the invention further enable the weight of the elements to be checked using the same weighing unit provided with a plurality of weighing cells, part of which are intended for measuring the weight of the empty elements, the remaining part intended for measuring the weight of filled elements. As these load cells are adjacent, during operation they are subject to the same environmental factors such as temperature, pressure, humidity, vibrations, electrostatic charges, electromagnetic waves, etc and are therefore possibly disturbed in the same manner in the measuring .

In addition to this, as the weighing unit, of known type, is provided with internal calibrating means to perform calibrating of the load cells at regular intervals, the latter have the same precision and accuracy in obtaining the weight. Possible measuring errors and/or deviations can, in fact, be eliminated or greatly reduced using the internal calibrating means that comprises an internal reference weighing cell that is able to provide a measurement of comparison on the basis of which to calibrate and/or adjust the weighing cells.

The weighing system is able to weigh and move a plurality of elements in a parallel manner at the same time, on the basis of the features of the dosing machine, thus ensuring the same high productivity of the latter. In a third aspect of the invention there is provided a device for varying a mutual distance of a group of adjacent elements, that is applicable to the system and/or to the aforesaid filling plant, comprising first drum means having a side wall provided with a plurality of guide means extending along said side wall so that a distance between adjacent guide means varies from a first value, at a first position of said first drum means, in which said elements are inserted into said guide means, to a second value, at a second position of said first drum means, in which said elements are extracted from said guide means, second drum means mounted rotatably on said first drum means and provided with at least an opening that is transverse to said guide means, suitable for receiving said group of elements, said second drum means rotating so as to move said group of elements along said guide means, between said first position and said second position.

Owing to this aspect of the invention it is possible to obtain a device that enables a group of adjacent and aligned elements to be transferred and a reciprocal distance thereof to be simultaneously varied so as to connect apparatuses or machines in which said elements are arranged with diverse pitches .

As the device can also operate continuously, by virtue of the rotation with continuous motion of the second drum means that moves a plurality of elements placed side by side along the guide means, it is possible to move a great number of elements over the unit of time. The device further enables an initial and/or final distance to be varied in an easy and fast manner and/or the number of guide means i.e. the elements that are movable in parallel at the same time to be varied in an easy and fast manner. It is in fact sufficient to replace the first fixed drum means bearing the guide means .

The invention can be better understood and implemented with reference to the attached drawings that illustrate some embodiments thereof by way of non-limiting example, in which: Figure 1 is a schematic plan view of a system for weighing elements according to the invention, in association with a filling machine of such elements; Figure 2 is a frontal schematic view of the system in Figure 1, which illustrates in particular a weighing apparatus and movement means for moving empty elements to be dosed entering said dosing machine;

Figure 3 is a frontal schematic view of the system in Figure 1 which illustrates in particular the weighing apparatus and further movement means for moving filled elements exiting said dosing machine; Figures 4 and 5 are partial and enlarged views of the system in Figure 2 ;

Figures 6 and 7 are partial and enlarged views of the system in Figure 3 ; Figure 8 is a partially sectioned schematic view of a transferring device of movement means in Figure 2; Figure 9 is a schematic and partial view of the device in Figure 8 unrolled on a plane; Figure 10 is a partially sectioned schematic view of a further transferring device of further movement means in Figure 3 ;

Figure 11 is a schematic and partial view of the further device in Figure 9 unrolled on a plane . With reference to Figures 1 to 7, there is illustrated a system 1 for weighing a dosed product inside elements 100, in particular elements or capsules of hard gelatine of the known cover-base type, by a filling machine 3, for example a capsule-filling machine 3. The system 1 comprises a weighing apparatus 2 provided with a weighing unit 20 arranged for weighing all the empty elements 100 to be transferred to said filling machine 3 and all the filled elements 100' with the product, exiting said filling machine 3. For this purpose, from what has been illustrated in Figures 1 and 7, the weighing unit 20 comprises at least a first weighing cell 25 for weighing the empty elements 100 and at least a second weighing cell 26 for weighing the filled elements 100' . In particular, the weighing unit 20 comprises a plurality of first load cells 25, for example six, and a plurality of second load cells 26, for example six, aligned and mutually regularly spaced away from one another .

The system 1 is further provided with processing means 10 connected to the weighing unit 20 and able to calculate for each filled element 100' the weight difference measured by said weighing unit 20 before and after filling, so as to determine with precision and accuracy the actual quantity of dosed product . The weighing apparatus 2 is of known type and disclosed in European Patent EP 886765 of the applicant, and comprises supplying means 11 for transferring said empty elements 100 from supplying hopper means 22 to the first weighing cells 25 (Figure 2) .

The supplying means 11 comprises conveying means 21 configured for conveying the empty elements 100, arranged aligned on at least a row, from said supplying hopper 22 to first wheel means 23 rotating and suitable for positioning each empty element 100 on a respective first weighing cell 25.

From what has been illustrated in Figures 1, 2 and 4, and with reference to the description of the aforesaid European Patent EP 886765, the first wheel means 23 is provided peripherally with a plurality of radially protruding reference teeth 23a, and with suction holes (not illustrated here) . The teeth 23a and the holes are angularly spaced along the external surface of the wheel 23 respectively to remove the elements 100 one at a time from the conveying means 21 and retain the elements 100 on said wheel means 23 during rotation. When the element 100 is positioned at a respective weighing cell 25, the suction of the first wheel means 23 is interrupted and the element 100 drops by gravity onto the load cell 25 to be subsequently weighed. The weight of each element 100 measured by the respective weighing cell 25 is sent by the weighing unit 20 to the processing means 10 that stores the weight of each element 100 and associates the weight of each element 100 with a corresponding element 100. Each element 100 is then removed from the load cell 25 and pushed into a respective outlet conduit 28 by a reference tooth 23a of the movement wheel 23 that simultaneously deposits a successive element 100 on the weighing cell 25. The apparatus 2 is configured so as to operate on a plurality N of files of elements 100, for example six as illustrated in Figure 1, removed from the supplying hopper 22 and conveyed parallel along respective supplying conduits 21a of the conveying means 21 to the first wheel means 23. The latter comprises reference teeth 23a and suction holes arranged on N parallel planes, so as to move simultaneously N elements 100 from the respective supplying conduits 11a and position N elements on respective weighing cells 25.

The number N of the elements 100 weighed simultaneously by the weighing apparatus 2 corresponds to the number of elements that are filled at each work step or cycle by the filling machine 3, the number being, for example, comprised between four and eleven.

The weighing unit 20 is a multiple weighing cells balance of known type, in particular of the type operating preferably with technology based on the principle of compensating magnetic force. This balance is provided with a plurality of weighing cells, suitable for measuring weights up to 20 g with a resolution up to 0.0001 g. This balance comprises internal calibrating means provided for periodically calibrating the weighing cells. The calibrating means includes a reference load cell 27 (Figure 4) , positioned inside the balance, next to the other cells 25, 26, and used for providing a measurement of comparison on the basis of which to calibrate and/or adjust, at set intervals of time, all the weighing cells. In this manner, possible measuring errors and/or measuring deviations to which the weighing cells may be subjected during operation are eliminated or noticeably reduced during operation, so as to ensure common and the same measuring precision and accuracy. The balance 20 is generally also provided with known means suitable for compensating vibrations of the weighing apparatus 2, caused by moving parts, actuators, etc, and/or constant and/or occasional vibrations of the ground on which said apparatus rests . The system 1 further comprises first movement means 4 for transferring the empty elements 100 exiting the weighing apparatus 2 to a supplying carousel 31 of the filling machine 3, of known type and disclosed for example in European patents EP 0825846 and EP 1135294 of the applicant (Figures 1, 2 and 3) . Second movement means 5 is on the other hand provided for transferring the filled elements 100' from a dosing carousel 32 of the filling machine 3 to the weighing apparatus 2 (Figure 3) .

From what has been illustrated in Figures 2, 4, 5 and 8, the first movement means 4 comprises a transferring device 6 suitable for transferring the empty elements 100 weighed by the weighing unit 20 to first conveying means 7 that conveys said elements 100 to the filling machine 3.

The transferring device 6 comprises guide means suitable for receiving the empty elements 100 placed side by side on N rows and coming from the respective load cells 25, through respective outlet conduits 28. The transferring device 6, by means of the rotation of an inner drum, takes the elements 100 to containing means 71 of the first conveying means 7. The containing means 71 comprises a plurality of bushes 71, each of which comprising N cavities 71a within which the empty elements 100 drop by gravity.

As explained in greater detail below in the description, the transferring device 6 is further able to vary, during rotation, a distance or pitch between the N rows of empty elements 100. This variation is necessary because generally the pitch between two load cells 25 is greater than the pitch between two adjacent elements in the supplying carousel 31 and in the filling carousel 32 of the filling machine 3. In the case in point, the transferring device 6 reduces the pitch between the adjacent empty elements 100. The bushes 71 are fixed to flexible means 72 of the first conveying means 7 , that are regularly spaced apart from one another along the movement direction of the latter. The flexible means 72 comprises, for example, a toothed belt wound in a closed loop around two pulleys 73, 74 at least one of which being a drive pulley and rotating in step with the transferring device 6. The first conveying means 7 transfers the elements 100 to a supplying carousel 31 of the filling machine 3, provided peripherally with seats suitable for receiving the empty elements 100. Opening means 33 {per se known) is provided for opening each empty element.100, consisting of a lower part and an upper part, and depositing the aforesaid lower part and upper part separately in respective housings of the dosing carousel 32. The aforesaid second movement means 5 comprises second conveying means 8 (Figures 6 and 7) suitable for receiving the filled elements 100' from the dosing carousel 32 of the filling machine 3 and transferring the filled elements 100' again to the weighing apparatus 2. The second conveying means 8 is substantially identical to the first conveying means 7 and comprises second flexible means 82 to which second containing means 81 are fixed that are regularly spaced apart from one another. The second containing means 81 comprises a plurality of second bushes 81, each of which comprising a plurality of respective cavities 81a that are adjacent and aligned transversely with respect to the advance direction of the second conveying means 8 , arranged for receiving and containing the N filled elements 100' exiting the dosing carousel 32. The further flexible means 82 comprises, for example, a respective toothed belt wound in a closed loop around two further pulleys 83, 84 at least one of which is a driving pulley and rotating in step with the dosing carousel 32. Extracting means 34 of pneumatic type is further provided for extracting the filled elements 100' from the filling carousel 32 and pushing the filled elements 100' through further conduit means 35 into the further containing bushes 81

(Figures 6 and 7) . The extracting means 34 comprises a plurality N of respective conduits 35 for moving at the same time N filled elements 100' . The second movement means 5, from what has been illustrated in Figures 7 and 10, comprises a further transferring device 60, substantially similar to the transferring device 6 of the first movement means 4 and arranged for transferring the filled elements 100' from the second conveying means 8 to second wheel means 24 of the weighing apparatus 2. The further transferring device 60 is provided with housings suitable for receiving the filled elements 100', placed side by side on N rows, released by the second bushes 81 of the second conveying means 82. A respective internal drum by rotating takes the filled elements 100' to respective sucking holes 24b of the second wheel means 24 (Figure 10) .

As explained in greater detail below in the description, also the further transferring device 60 is suitable for varying, during rotation, the pitch between the N rows of filled elements 100' : in the case in point, it increases the pitch between the adjacent filled elements 100' .

The second wheel means 24, which is substantially identical to the first wheel means 23, transfers and deposits the filled elements 100' on the aforesaid respective second weighing cells 26 of the weighing unit 20, which measures the gross weight of each filled element 100' . The value of the gross weight of each filled element 100' is then sent by the weighing unit 20 to the processing means 10, which associates this value with the corresponding weight value of the empty element 100, so as to calculate by difference the net weight of the dosed product.

Respective reference teeth 24a of the second wheel means 24 remove the filled elements 100' from the second weighing cells 26 and push the filled elements 100' into a first collecting container 40, by means of first slide means 29 (Figures 1, 3 and 7) .

Deflecting means, which is of known type and is not shown, is provided for deviating the filled elements to be rejected because they are non-standard, to a second collecting container 41, by means of second slide means 44. Alternatively, the filled elements 100' can be conveyed by means of slide means and conveying means known and not illustrated to a packaging machine, for example a blistering machine .

It is appropriate to observe that the system for weighing elements of the invention, comprises a weighing unit provided with a plurality of weighing cells, a part of which - first weighing cells 25 - intended for measuring the weight of the empty elements, the remaining part - second weighing cells 26 - being intended for measuring the weight of the filled elements. By virtue of the features of this weighing unit 20, which is provided with internal calibrating means, the load cells 25, 26 have the same precision and accuracy in detecting the weight, as possible errors and/or deviations can be virtually eliminated, or greatly reduced, by the control by means of the internal reference cell. The processing means 10 is connected to control means 37

(Figure 1) of the filling machine 3 so as to follow the path of the elements 100, 100' through the system 1 and in particular associate with each element the two weight values before and after filling. With particular reference to Figures 8 and 9, there is illustrated the transferring device 6 that comprises a first fixed drum 12, having an external side wall 12a, on which guide means 13 is made comprising a plurality of longitudinal grooves 13. The number of guiding grooves 13 depends on the aforesaid number N of elements 100 moved in a parallel manner and at the same time from the system 1 i.e. the number of the elements filled at each cycle by the filling machine 3. A second drum 14 is mounted on the first fixed drum 12, coaxially to the latter and rotatably with respect to a substantially horizontal longitudinal axis X.

The second drum 14 comprises a cylindrical wall 14a provided with a plurality of transverse openings 15 and having a thickness that is less than a longitudinal dimension, or height, of the element 100. The transverse openings 15 are through, elongated and rectilinear slots, arranged transversely to. the guiding grooves 13 and substantially parallel to the axis X. As illustrated in Figure 9, the guiding grooves 13 extend along the external side wall 12a of the first fixed drum 12, so that a pitch or distance between two adjacent grooves can vary from a first value Pl, at a first angular position A of said first fixed drum 12, to a second value P2, at a second angular position B of said first fixed drum 12. The first value Pl coincides substantially with the pitch between two adjacent weighing cells 25, i.e. between the rows of the empty elements 100 in the weighing apparatus 20. The angular position A of the first fixed . drum 12 corresponds to the point in which said empty elements 100, coming from the outlet conduits 28, are introduced into the transferring device 6. The second value P2 substantially coincides with the pitch between two elements 100, 100' adjacent in the supplying carousel 31 and in the dosing carousel 32 of the filling machine 3. The angular position B of the first fixed drum 12 corresponds to the point in which the elements 100 are released into the cavities 71a of the bushes 71. The angular positions A, B, and thus the extent of the guiding grooves 13 , depend on the arrangement of the transferring device 6 with respect to the outlet conduits 28 and to the first conveying means 7. In the embodiment shown in Figure 8, the first angular position A and the second angular position B are angularly spaced apart, in a clockwise direction, by an angle equal to approximately 210°. The transverse openings 15 are regularly angularly spaced apart by a preset angle, for example 30°, calculated on the basis of operational and/or geometric parameters of the system 1, such as, for example, the interval of time between one weighing and the other, the rotation speed of the transferring device 6, dimensions of the latter, etc. The transferring device 6 further comprises a third drum 16 mounted on the second drum 14 , coaxial to the latter and to the first fixed drum 12 and fixed with respect to the axis X. The third drum 16 has a respective side wall having a thickness that is substantially similar to that of the second drum 14 and provided internally with a plurality of further guiding grooves 17 suitable for defining in cooperation with the guiding grooves 13 of the first fixed drum 12 a plurality of closed conduits, for housing and conveying the elements 100.

The third drum 16 further comprises first openings 18 that enable the elements 100 to be inserted inside the guiding grooves 13, 17 and second openings 19 for the exiting of said elements 100 from the guiding grooves 13, 17. The first openings 18 and the second openings 19 are made respectively at the first angular position A and at the second angular position B of the first drum 12. At each first opening 18, in the first fixed drum 12 a respective sucking conduit 42 can be in flow connection with a sucking source of the air, for example a vacuum pump, to facilitate the introduction of each element 100 inside the transferring device 6. Similarly, at each second opening 19 in the first fixed drum 12 a respective expulsion conduit 43 can be provided flowingly connected to a source of pressurised air in order to facilitate the expulsion of each element 100 from the transferring device 6.

The operation of the transferring device 6 provides for a plurality N of empty elements 100 coming from the load cells 25 and arranged on parallel rows, mutually spaced apart by a first value Pl, being inserted into the transferring drum 6 at the first angular position A, in which the guiding grooves 13, 17 are spaced apart from one another by said first value Pl. When the empty elements 100 are inserted, the second drum 14 rotating around the axis X is positioned angularly so that a transverse opening 15 faces the outlet conduits 28. In this manner, each element 100 can be inserted inside a respective guide groove 13 , which receives a bottom portion thereof and inside said transverse opening 15, which abuts on a central portion thereof . The subsequent rotation of the second drum 14 around the axis X, for example clockwise, determines the movement along the respective guiding grooves 13, 17 of the empty elements 100. By virtue of the conformation of said guiding grooves 13, 17, in the rotation of the second drum 14 from the first angular position A to the second angular position B, the empty elements 100 run transversely inside the through openings 15, so as to mutually approach one another up to a distance equal to the second value P2, distance or pitch with which they are removed from the transferring device 6 and inserted into the respective bushes 71 of the first conveying means 7. With reference to Figures 10 and 11, there is illustrated the further transferring device 60 of the second movement means 5 that transfers the filled elements 100' from the second conveying means 8 to the second wheel means 24 of the weighing apparatus 2.

The further transferring device 60 differs from the transferring device 6 disclosed above substantially for the different configuration and extent of the guiding grooves, arranged for returning the distance or pitch of the filled elements 100' from the second value P2 to the first value Pl. The further transferring device 60 thus comprises a further first fixed drum 62 having a respective cylindrical external side wall 62a on which further guide means 63 is made, comprising a plurality of respective longitudinal guiding grooves. The number of such guiding grooves 63 depends on the number N of elements 100 conveyed by the second conveying means 8 i.e. filled at each cycle by the filling machine 3. A further second drum 64 is mounted on the further first fixed drum 62, coaxially to the latter and rotatable with respect to a further rotation axis X' . The further second drum 64 has a respective cylindrical side wall 64a having a thickness that is less than a longitudinal dimension, or height, of the filled element 100' and provided with a plurality of transverse openings 65. Such transverse openings 65 are through, elongated and rectilinear slots, arranged transversely to the respective guiding grooves 63 and substantially parallel to the further axis X' .

As illustrated in Figure 11, the respective guiding grooves 63 extend around the side wall 62a of the further first fixed drum 62, so that the pitch between two adjacent guiding grooves 63 can vary from the second value P2 at a further first angular position C of said further first fixed drum 62, to first value Pl, at a further second angular position D of said further first fixed drum 62. The further first angular position A corresponds to the point at which the filled elements 100' , dropping by gravity from the respective second bushes 81, is introduced into the further transferring device 62. The further second angular position D corresponds to the point at which the filled elements 100' are released by the second wheel means 24.

The further angular positions C, D, and thus the development of the respective guiding grooves 63, depend on the arrangement of the further transferring device 60 with respect to the second conveying means 8 and to the second wheel means 24. In the embodiment shown in Figure 10, the further first angular position C and the further second angular position D are spaced angularly apart, in an anticlockwise direction, by an angle of about 210°. The further through transverse openings 65 are angularly spaced by a preset angle, for example 30°, calculated in function of the operating parameters and/or geometrical parameters of the system 1, such as, for example, the lapse between one weighing and another, rotation speed of the further transferring device 60, dimensions of the latter, etc.

A further third drum 66 is further provided having a semicylindrical shape, mounted around a portion of the further second drum 64 , coaxial to the latter and to the further first fixed drum 62 and fixed with respect to the axis X' .

The further third drum 66 has a respective side wall having a thickness substantially similar to that of the further second drum 64 and provided internally with a plurality of respective further guiding grooves 67 configured so as to form in cooperation with the respective first guiding grooves 63 of the further first fixed drum 62 a plurality of respective closed conduits, suitable for housing and conveying the filled elements 100' between the further first angular position C and the further second angular position D. The further third drum 66 further comprises respective openings 68, made at the further first angular position C, which enables the filled elements 100' to be inserted inside the further guiding grooves 63.

The operation of the further transferring device 60 is substantially identical to that of the transferring device 6 disclosed previously, from which it differs by the fact that in this case the plurality of filled elements 100' coming from the^ second conveying means 8 and inserted into the further grooves 63, 67 are spaced apart from one another by a pitch equal to the second value P2 and are progressively spaced apart, dragged by the rotation of the further second drum 64, to a pitch equal to the first value Pl. It should be emphasised that the number of guiding grooves 13, 17, 63, 67 that are makable respectively on the first drums 12, .62 and on the third drums 16, 66 is a function of the features of the filling machine 3.

The transferring devices 6, 60 thus enables a group of adjacent and aligned elements 100, 100' to be transferred and at the same time a mutual distance to be maintained, so as to connect apparatuses or machines in which said elements 100, 100' are arranged with various pitches.

As the transferring devices 6, 60 can also operate continuously, with the respective second drum 14, 64 rotating around the axis X, X' at a continuous speed, on a plurality of elements placed side by side, for example from 4 to 11, it is possible to move a very high number of products over the unit of time. In order to vary the initial and/or final distances of the elements 100, 100' and/or the number of guiding grooves 13, 17, 63, 67 it is further sufficient to replace the first fixed drum 12, 62 and the third drum 16, 66, which are both fixed and couplable, in a rapid and simple manner, with a carrying structure of the transferring device 6, 60.

Claims

1. System (1) for weighing a product dosed in elements (100) , in particular capsules (100) of hard gelatine of the cover-base type, by a filling machine (3) , comprising a weighing apparatus (2) , first movement means (4) for transferring empty elements (100) from said weighing apparatus (2) to said filling machine (3) and second movement means (5) for transferring filled elements

(100') with said dosed product from said filling machine (3) to said weighing apparatus (2), said weighing apparatus (2) comprising a weighing unit (20) for weighing each empty element (100) and each filled element

(100'), processing means (10) connected to said weighing unit (20) for receiving data relating to weights measured by the latter and calculating for each element (100') a difference of weight measured before and after filling so as to determine a respective quantity of actually dosed product.

2. System according to claim 1, wherein said weighing unit (20) comprises at least a first weighing cell (25) for weighing empty elements (100) and at least a second weighing cell (26) for weighing elements (100') filled with said product.

3. System according to claim 2, wherein said weighing unit (20) comprises internal calibrating means for calibrating said weighing cells (25, 26) .

4. System according to claim 3, wherein said calibrating means comprises a reference load cell (27) , placed inside said weighing unit (20) adjacent to said weighing cells (25, 28) , said reference cell (27) being suitable for providing a measure of comparison on the basis of which to calibrate said weighing cells (25, 26) .

5. System according to any one of claims 2 to 4, wherein said weighing unit (20) comprises a plurality of first load cells (25) and a plurality of second load cells (26) , that are aligned and mutually spaced apart from one another .

6. System according to any one of claims 2 to 5, wherein said weighing apparatus (2) comprises supplying means (11) for transferring said empty elements (100) from supplying hopper means (22) to said first weighing cell (25) .

7. System according to claim 6, wherein said supplying means (11) comprises conveying means (21) for conveying said empty elements (100) , arranged aligned on at least a row, from said hopper means (22) to first wheel means (23) rotating and suitable for positioning each empty element (100) on a respective first weighing cell (25) .

8. System according to any one of claims 1 to 7, wherein said first movement means (4) comprises a transferring device (6) arranged for transferring said empty elements (100) exiting said weighing unit (20) to first conveying means (7) configured for conveying said empty elements (100) to said filling machine (3) .

9. System according to any one of claims 1 to 8, wherein said second movement means (5) comprises second conveying means (8) for receiving and conveying said filled elements (100') from said filling machine (3) to said weighing apparatus (2) .

10. System according to claim 9, wherein said second movement means (5) comprises a further transferring device (60) for transferring said filled elements (100') from said second conveying means (8) to said weighing unit (20) .

11. System according to claim 10, wherein said weighing apparatus (2) comprises second wheel means (24) that rotates and is suitable for receiving each filled element (100') from said further transferring device (60) and transferring the filled element (100') to a respective second weighing cell (26) .

12. System according to any one of claims 8 to 11, wherein said conveying means (7, 8) comprises belt means (72,

82) , wound in a closed loop on pulley means (73, 74, 82, 84), and containing means (71, 81) of said elements (100, 100') connected to said belt means (72, 82).

13. System according to claim 12, wherein said containing means (71, 81) comprises a plurality of bushes fixed to said belt means (72, 82) mutually spaced apart along a movement direction of said belt means (72, 82) .

14. System according to claim 13, wherein each bush (71, 81) comprises a set of cavities (71a, 81a) each of which is suitable for housing a respective element (100, 100').

15. System according to claim 8 or 10, wherein said transferring device (6; 60) comprises first drum means

(12; 62) having a side wall {12a.; 62a) provided with a plurality of guide means (13; 63) extending along said side wall (12a; 62a) so that a distance between adjacent guide means (13; 63) varies from a first value (Pl), at a first position (A; C) of said first drum means (12; 62), wherein a group of elements (100; 100') is inserted into said guide means (13; 63), to a second value (P2) , at a second position (B; D) of said first drum means (12; 62), wherein said group of elements (100; 100' ) is extracted from said guide means (13; 63), second drum means (14; 64) mounted rotatably on said first drum means (12; 62) and provided with at least an opening (15; 65) that is transverse to said guide means (13; 63), and suitable for receiving said group of elements (100; 100' ) , said second drum means (14; 64) rotating so as to move said group of elements (100; 100') along said guide means (13; 63), between said first position (A; C) and said second position (B; D) varying a mutual distance between said group of adjacent elements (100; 100') from said first value (Pl) to said second value (P2) or vice versa.

16. System according to claims 5 and 15, wherein said plurality of first weighing cells (25) and of second weighing cells (26) are mutually spaced apart from one another by said first value (Pl) .

17. System according to claim 15 or 16, wherein said elements (100; 100') are mutually spaced apart inside operating means (3I₇ 32, 33, 34) of said filling machine (3), by- said second value (P2) .

18. System according to claim 17, wherein said second drum means (14; 64) is arranged externally and coaxially to a said first drum means (12; 62) .

19. System according to claim 18, comprising third drum means (16; 66) mounted externally to said second drum means (14; 64) and configured for maintaining said elements (100; 100' ) inside said guide means (13; 63) during a rotation of said second drum means (14; 64), between said first position (A; C) and said second position (B; D) .

20. System according to claim 19, wherein said third drum means (16; 65) comprises first openings (18; 68) for inserting said elements (100; 100') into said transverse opening (15) and said plurality of guide means (13; 63), at said first position (A; C) .

21. System according to claim 19 or 20, wherein said third drum means (16) comprises second openings (19) for the exiting of said elements (100) from said device (6) , at said second position (B) .

22. System according to claim 20, comprising first conduit means (42) provided in said first drum means (12) at said first openings (18) and connected to sucking means for promoting the insertion of said elements (100) inside said device (6) .

23. System according to claim 21, comprising second conduit means (43) provided in said first drum means (12) at said second openings (19) and connected to blowing means for promoting the exiting of said elements (100) from said device (6) .

24. System according to any one of claims 15 to 23, wherein said plurality of guide means (13; 63) comprises a plurality of grooves made in an external portion of said side wall (12a; 62a) .

25. System according to claim 24, as appended to any one of claims 19 to 23, wherein said third drum means (16; 66) comprises a respective side surface provided with a plurality of further guiding grooves (17; 67) extending so as to form with said guiding grooves (13; 63) of the first drum means (12; 62) a plurality of conduits suitable for housing and conveying said elements (100; 100' ) .

26. System according to any one of claims 15 to 25, wherein said transverse opening (15; 65) is made on a respective side wall (14a; 64a) of said second drum means (14; 64) .

27. System according to any one of claims 15 to 26, wherein said transverse opening (15) comprises a rectilinear through slot, substantially parallel to a rotation axis (X; X') of said second drum means (14) .

28. System according to claim 26, wherein said second drum means (14) comprises a plurality of openings (15; 65) regularly spaced apart along said respective side wall (14a; 64a) .

29. System according to any one of claims 26 to 28, as claim 27 is appended to claim 26, wherein said respective side wall (14a; 64a) of said second drum means (14; 64) has a thickness that is less than a longitudinal dimension of said elements (100; 100').

30. Method for weighing a product dosed in elements (100), in particular capsules of hard gelatine of the cover-base type, by a filling machine (3) , comprising the steps of weighing empty elements (100) to be dosed by a weighing unit (20) , transferring said weighed empty elements (100) to said filling machine (3) , transferring filled elements^' (100' ) from said filling machine (3) to said weighing unit (20) , weighing said filled elements (100' ) by means of said weighing unit (20) , calculating for each filled element (100') a difference of weight measured before and after filling from said weighing unit (20) so as to determine a respective quantity of actually dosed product .

31. Method according to claim 30, comprising the step of weighing at the same time a plurality of empty elements (100) and a plurality of filled elements (100') by means of respectively a plurality of first weighing cells (25) and a plurality of second weighing cells (26) of said weighing unit (20) .

32. Method according to claim 31, comprising the step of calibrating said weighing cells ^" (25, 26) by internal calibrating means of said weighing unit (20) .

33. Method according to claim 32, wherein said calibrating comprises comparing measurements made by said weighing cells (25, 26) with a reference measurement detected by a reference load cell (27) , placed inside said weighing unit (20) and adjacent to said weighing cells (25, 28) .

34. Method according to claim 32 or 33, comprising calibrating said weighing cells (25, 26) at regular and defined intervals .

35. Device, in particular applied to the system (1) according to one or more of preceding claims 1 to 29, to vary a mutual distance of a group of adjacent elements (100) , comprising first drum means (12; 62) having a side wall (12a; 62a) provided with a plurality of guide means (13; 63) extending along said side wall (12a; 62a) so that a distance between adjacent guide means (13; 63) varies from a first value (Pl) , at a first position (A; C) of said first drum means (12; 62), wherein said elements (100) are inserted into said guide means (13; 63), to a second value (P2) , at a second position (B; D) of said first drum means (12; 62), wherein said elements (100) are extracted from said guide means (13; 63), second drum means (14; 64) mounted rotatably on said first drum means

(12; 62) and provided with at least an opening (15; 65) that is transverse to said guide means (13; 63), suitable for receiving said group of elements (100) , said second drum means (14; 64) rotating so as to move said group of elements (100) along said guide means (13; 63), between said first position (A; C) and said second position (B; D) .

36. Device according to claim 35, wherein said second drum means (14; 64) is external and coaxial to said first drum means (12; 62) .

37. Device according to claim 36, comprising third drum means

(16; 66) mounted externally to said second drum means

(14; 64) and configured for maintaining said elements

(100) inside said guide means (13; 63) during a rotation of said second drum means (14; 64), between said first position (A; C) and said second position (B; D) .

38. Device according to claim 37, wherein said third drum means (16; 66) comprises first openings (18; 68) for inserting said elements (100) into said transverse opening (15; 65) and into said plurality of guide means (13; 63), at said first position (A; C).

39. Device according to claim 37 or 38, wherein said third drum means (16) comprises second openings (19) for the exiting of said elements (100) from said guide means (13; 63) , at said second position (B) .

40. Device according to claim 38, comprising first conduit means (42) provided in said first drum means (12) at said first openings (18) and connected to sucking means for promoting the insertion of said elements (100) inside said guide means (13; 63) .

41. Device according to claim 39, comprising second conduit means (43) provided in said first drum means (12) at said second openings (19) and connected to blowing means for promoting the exiting of said elements (100) from said guide means (13; 63) .

42. Device according to any one of claims 35 to 41, wherein said plurality of guide means (13; 63) comprises a plurality of grooves made in an external portion of said side wall (12a; 62a) .

43. Device according to claim 42, as appended to any one of claims 37 to 41, wherein said third drum means (16; 66) comprises a respective side wall provided with a plurality of further guiding grooves (17; 67) extending so as to form with said guiding grooves (13_/ 63) of the first drum means (12; 62) a plurality of conduits suitable for housing and conveying said elements (100) .

44. Device according to any one of claims 35 to 43, wherein said transverse opening (15; 65) is made on a respective side wall (14a) of said second drum means (14) .

45. Device according to any one of claims 35 to 44, wherein said transverse opening (15; 65) comprises a rectilinear through slot, substantially parallel to a rotation axis (X; X') of said second drum means (14) .

46. Device according to claim 44, wherein said second drum means (14; 64) comprises a plurality of openings (15; 65) regularly spaced apart along said respective side wall (14a; 64a) .

47. Device according to any one of claims 44 to 46, as claim 45 is appended to claim 44, wherein said respective side wall (14a; 64a) of said second drum means (14; 64) has a thickness that is less than a- longitudinal dimension of said elements (100) .

48. Plant for filling a product dosed in elements (100), in particular capsules (100) of hard gelatine of the cover- base type, comprising a filling machine (3) of said elements (100) coupled with a weighing system (1) according to one or more of preceding claims 1 to 29.

49. Plant according to claim 48, comprising the device according to any one of claims 35 to 47.