WO1996020390A1

WO1996020390A1 - Method and apparatus for checking the weight of small articles

Info

Publication number: WO1996020390A1
Application number: PCT/EP1995/004925
Authority: WO
Inventors: Aristide Cane'; Angiolino Ribani
Original assignee: I.M.A. Industria Macchine Automatiche S.P.A.
Priority date: 1994-12-23
Filing date: 1995-12-13
Publication date: 1996-07-04
Also published as: ITBO940573A1; ITBO940573A0; ZA9510503B; TW288102B; IT1273862B

Abstract

The articles, such as capsules, are fed in single file and singly into a centrifuging system (1) whose speed and radius of rotation are known, and each centrifuged capsule is caused to interact with at least one transducer (13) capable of measuring the centrifugal force exerted by the capsule which is then released and discharged. The signal produced by the said transducer is processed by a unit (14) which measures the actual weight of the capsule, compares it with acceptability parameters and may cause the activation of a device (18) capable of separating the capsules of acceptable weight from those of unacceptable weight.

Description

"METHOD AND APPARATUS FOR CHECKING THE WEIGHT OF SMALL ARTICLES"

DESCRIPTION

The invention relates to high-output production machines for the production of small articles, such as for example capsule fillers designed for filling gelatine capsules with pharmaceutical or other types of products, or to machines designed for the production of tablets for pharmaceutical or nutritional use. For convenience, reference will be made in the following text to capsule fillers and to capsules only, but without excluding any other type of machine or product.

The weight of the capsules filled by capsule fillers has to be checked, and this problem, owing to the very high output of existing capsule fillers and the use of static weight checking systems, is currently resolved by dividing the output of the machine into batches and subjecting the capsules of each batch to statistical weight checking which progressively measures the behaviour of all the working stations of the capsule filler. If the statistical weight check does not find values falling outside the specified tolerances, the batch is authorized for the subsequent stages of work, for example for packaging or other operations, while, in the contrary case, the batch is isolated and its con¬ stituent capsules may be rejected or weighed slowly one by one by meεuis of automatic equipment in such a way that the rejection is limited to the capsules of incorrect weight only.

Evidently, the existing solutions for checking the weight of filled capsules are not absolutely reli¬ able, since the capsules are checked statistically and not individually.

Attempts have been made to check the weight of all the filled capsules produced by a capsule filler, using a dynamic weighing system. For example, there is a known dynamic weighing process in which the capsules are made to pass in single file through an electrical field, while suitable means find variations of the said field, for example variations of capacitance which may vary as a function of the total dielectric mass of the capsule and the product contained in it. However, this process is not reliable and is not suitable for industrial applica¬ tion, since the measurements made may be modified by variations of temperature and/or ambient humidity, and by the type and/or location of the product inside the capsule.

The invention proposes the following process for the dynamic, rapid checking of the weight of filled capsules produced by a capsule filler.

The weight of the capsule is amplified by centri- fuging by means of a system in which the speed of rota¬ tion and the radius of rotation of the capsule is known and any suitable transducer is used to measure the centrifugal force exerted by the capsule being rotated, and to generate an electrical signal proportional to this parameter, which will be directly proportional both to the weight of the capsule and to the square of the speed of rotation of the capsule, and which will therefore increase with the said speed of rotation. Since the amplification parameters associated with the rotation are known, it will be possible to retrieve, by simple elec¬ tronic processing of the signal produced by the said transducer, a signal corresponding to the actual weight of the capsule which has been centrifuged and then discharged. This signal of the actual weight is compared electronically with specified limit values and the result of this comparison may be used to activate or disable means for dividing the capsules of acceptable weight from those of incorrect weight, or may be used for other purposes. The advantages derived from this process may be summarized as follows: a) the weight variations for which a filled capsule may be considered acceptable or unacceptable are of the order of a few milligrams, and in measuring^* these values ordinary weighing systems would be affected by the vibrations caused by the means used to move the capsules. With the process according to the invention, the weight of the capsule can be amplified and a physical quantity of a dynamic type (centrifugal force) , proportional to the weight and of a size much greater than the dynamic disturbance caused by the vibrations of the capsule movement systems, can be measured, so that the amplified weight signal is separated from the disturbance (noise) signal and can easily be found in the peak values; b) . the new process is suitable for the use of a trans¬ ducer for dynamic measurement of the centrifugal force exerted by the capsules being rotated, the said trans¬ ducer not being mounted on the capsule rotation system and therefore capable of being isolated from the vibra¬ tions induced by the said rotation system; c) the new process is suitable for checking the weight of a fast flow of capsules, for example up to the order of 1500-2000 per minute, and therefore may be used to measure in real time the weight of the capsules produced by existing high-output carousel-type capsule fillers; d) the new process is of a purely electromechanical type, of high reliability, and is therefore more capable of dependable industrial application. The electronic processing systems for the data from the centrifugal force transducer may allow for any variations in real time of the speed of rotation of the weighed capsules and may modify their operation in the presence of such variations.

Further characteristics of the invention, and the advantages derived therefrom, will be more clearly understood from the following description of some prefer¬ red embodiments of the invention, illustrated by way of example in the figures of the attached sheets of dra¬ wings, in which

Fig. 1 is a schematic plan view from above, with parts in section, of a first embodiment of the apparatus according to the invention;

Fig. 2 is an illustration of the apparatus shown in Figure 1, in section along the line II-II;

. Fig. 3 shows, in the same view as that of Figure 2, a modified embodiment of the apparatus. Figures 1 and 2 show that the apparatus comprises a rotor 1 consisting of a wheel or of two opposing spokes, keyed to a vertical shaft 2 supported rotatably on bearings 3 by a horizontal fixed plate 4, the rotor having a circular shape in plan and being provided on its perimeter with a raised containing wall 5, which has a first portion 105 whose inner wall is at a short distance from the ends of the said rotor, and a second portion 205 whose inner wall is more distant from the ends of the rotor, and which is broken for an interrupted portion 305 of precise extent.

The opposing spokes of the rotor 1 have a lateral profile in the form of a double incline and are joined to an axial raised part 101 as shown in Figure 2, this part having an axial channel 6 whose diameter is suitably greater than the external diameter of the capsules 10 which are to be weighed and which are fed by known means 7 in single file into the- said channel, with a random orientation or with a constant and predetermined orienta¬ tion, for example with all having their bases or lids orientated forwards. The channel 6 continues downwards with a curved profile 106 which extends along one of the spokes of the rotor 1 and which terminates at the end of the said spoke, with a substantially horizontal portion 206 whose length is substantially equal to that of one capsule and is divided from the preceding channel by a transverse slit 8, which passes partly through the spoke of the rotor and opens downwardly, for example, and which when seen in plan is in the form of an arc with its centre on the axis of the shaft 2. During the rotation of the rotor in the direction shown in Figure 1 by the arrows 9, the slit 8 is engaged by a curved blade 11 integral with the plate 4 and having, in plan, the form of an arc of a circle whose centre is on the axis of the shaft 2. The blade 11 begins with a preferably tapered end 1110 next to the linking area 12 of the portions 105- 205 of the inner wall of the containing wall 5 (see below) and terminates after the opening 305 of the said wall.

At the end of the portion 205 of the wall 5 and as a coplanar extension of it, or in another suitable disposition, there is provided at least one weighing transducer 13, of any suitable type, for example an accelerometer of a single- or multiple-axis type, con¬ nected to a logical processing unit 14 with a correspond¬ ing power supply input 15, the processing unit being preferably designed to find the phase and speed of rotation of the rotor 1 with connection to the mechanism

16 for rotating the said rotor and, by operating accord¬ ing to a predetermined algorithm, providing at its output

17 an electrical signal proportional to the weight of the capsule 10 at the moment at which it passes, and is in contact with, the transducer 13. If there is more than one transducer, and they are contacted in sequence by the centrifuged capsule, the unit 14 finds the mean of the values acquired by the different transducers.

The operation of the just described apparatus is simple and evident. The rotor 1 rotates continuously in the -direction indicated by the arrow 9, at a predeter¬ mined and constant speed. The capsules 10, fed in single file into the channel 6, desc&nd by gravity and are carried by centrifugal force towards the terminal portion 206 of the said channel, where they are retained by bearing on the containing wall 5. During the rotation of the rotor in the direction 9, the leading capsule of the file is separated from the following one by the insertion of the blade 11 between the said capsules, the said insertion being facilitated by the tapered end shape 1110 of the said blade and possibly also by a blast of air supplied from the said end which will be provided with suitable internal ducts (not illustrated) connected to a source of compressed air, the whole being done in a way which can be understood and easily carried out by those skilled in the art. Exactly at the time of the insertion of the end 111 of the blade 11 between the capsules, the spoke of the rotor which carries the capsules ceases to interact with the portion of wall 105 and begins to interact with the wider portion 205 of the same wall 5, so that the leading capsule separated from the others and disposed outside the separating blade 11, is suitably distanced from the said blade, and continues to bear only on the wall 5. In its rotation on the wall 5, the separa¬ ted capsule is charged with potential energy as a result of the rotation, and when the said capsule interacts with the sensor 13 the latter finds the centrifugal force exerted on it by the capsule and converts this into a proportional electrical signal.

After the interaction with the transducer 13, the capsule which is present in the terminal portion 206 of the channel 6 of the rotor encounters the interruption 305 in the containing wall and leaves the rotor under the action of centrifugal force, passing for example across a source 18 of compressed air which may be activated at the command of the unit 14. The signal produced by the transducer 13 during the passage of the capsule 10 over the transducer is processed by the unit 14, which finds the actual weight of the capsule and compares it with predetermined acceptable values. If the weight found is correct, the source 18 remains inactive, while in the contrary case it is activated to strike the capsule of unacceptable weight with a jet of air which makes it deviate from the trajectory of the capsules of correct weight and forces it to fall into a separate area.

It is to be understood that other solutions may be used to separate the capsules of correct weight from those of unacceptable weight, and it is also to be understood that the apparatus according to the invention shall be considered to be protected even if used, in combination with the aforesaid separation, for other purposes, for example to provide automatic regulation of measured capsule filling machines.

The inactive spoke of the rotor is also provided with a transverse slit 8 to prevent interference with the blade 11 and is provided with recesses 100 for the dynamic balancing of the rotor.

The modified embodiment shown in Figure 3 has a rotor 1 designed to contain at least one channel 6 presenting a sinuous path 306, which terminates at the containing wall 5 in a portion 406 which is substantially vertical and is open outwardly with a "U"-shaped profile and is closed by the said wall 5. In this case, the separating blade 111 is disposed horizontally, is inte¬ gral with the top of the wall 5, and interacts with the transverse slit 108 which divides the said portion 406 of the channel 6 and which in this case is open outwardly. The capsule which comes into contact with the wall 5 and which is separated from those above it by the blade 111 is removed from the said blade by a small step formed on the surface of the plate 4, the whole being done in a way which can be conceived and easily carried out by those skilled in the art. The variant shown in Figure 3 makes the capsules cooperate with the sensor 13 with a lateral contact and not with an end contact as in the preceding solution.

It is to be understood that the description refers to certain preferred embodiments of the invention, to which numerous variations and modifications may be made, particularly in respect of construction. The capsules may be distributed in a different way in two channels located on both the opposing spokes of the rotor. The rotor with opposing spokes may be replaced with a wheel, to avoid the fan effect of the spokes and the formation of air currents which might disturb the operation of the transducer 13. The capsule to be weighed may be distanced from the separating blade 11 by a suitable shaping of the surfaces of the separating blade facing the said capsule, in combination with, or as an alternative to, the step 12. The transducer 13 may be of any type suitable for the purpose and may detect the centrifugal force of the capsule directly or with the interposition of other means, such as means of amplifying the said centrifugal force, compensating means, or others. The transducer 13 may be of the static or of the dynamic type.

Claims

1) Method for checking the weight of small articles coming from a high-output production machine, characterized by the fact of comprising the following steps:

- smgularization of the articles and centrifugation of each single article along a predetermined circular path around an ax s of rotation at a predetermined speed;

- measurement of the value of the centrifugal force imparted to each article and processing the said value of the centrifugal force to obtain a value corresponding to the weight;

- discharge of the single article by effect of the said centrifugation.

2) Method according to claim 1, characterized by the further step of comparing; the value corresponding to the weight with a predetermined value, for generating a control signal for sorting the articles of acceptable weight from those of unacceptable weight.

3) Method according to claim 1, in which the speed of centrifugation of the articles is such that the centrifugal force to which the articles are subjected is greater than the dynamic disturbances caused by the rotation of the articles, so that the said centrifugal force can be detected and measured in its peak values.

4) Method according to claim 1, in which the centrifuged articles are oblong articles and are arranged with a constant and predetermined orientation when the measurement of the value of the centrifugal force takes place.

5) Method according to claim 4, in which the articles are orientated with their longitudinal axes substantially perpendicular to the axis of rotation.

6) Method according to claim 4, in which the articles are orientated with their longitudinal axes substantially parallel to the axis of rotation.

7) Apparatus for checking the weight of small articles coming from a high-output production machine, characterized by the fact of comprising:

- centrifugation means (1) to cause the rotation of the articles (10) to be weighed, singly, on a circumference of constant radius and at a constant speed;

- feeding means (106, 306, 8, 108, 11, 111, 5) for feeding the articles (10) singly to the said centrifugation means (1) ;

- measurement means (13) for measuring the centrifugal force of each single centrifuged article (10);

- processing means (14) for processing the signal from the said measurement means (13) to obtain a value corresponding to the weight of the article;

- discharge means for discharging the centrifuged article (10) after the measurement of its centrifugal force.

8) Apparatus according to claim 7, characterized by the fact of further comprising comparator means (14) for comparing the value corresponding to the weight of the article (10) to a predetermined value and for generating a control signal controlling the operation of a sorting device (18) for sorting the articles of acceptable weight from those of unacceptable weight.

9) Apparatus according to claim 7 characterized by the fact of comprising:

- a rotor (1) rotating on a vertical axis (2) and presenting an axial channel (6) into which the articles (10) are fed in single file, said channel (6) having a suitably linked profile (106, 306) extending radially to the periphery of the rotor where it terminates with a final portion (206, 406) whose length is substantially equal to that of one article, said terminal portion being divided from the preceding portion of the channel by a transverse partial slit (8, 108);

- a fixed containment wall (5, 105, 205) provided on the periphery of said rotor for the containment of the centrifuged articles (10) in the channel (206, 406), said containment wall presenting an interrupted portion (305) for permitting the discharge of the articles;

- a fixed separator element (11) shaped like a curved blade capable of being inserted into the said transverse slit (8, 108) upon rotation of the rotor, so as to separate the article which is in contact with the said contaiment wall (205) from the articles located upstream in the channel, said separator element extending over an arc of circumference coaxial to the rotor axis such as to permit the separation of the single terminal article from the upstream articles in the channel, the discharge of only the said terminal article at the interrupted portion (305) of the containment wall (5) while keeping the other articles in the upstream portion of the channel (106, 306), and the subsequent advancement of another single article (10) into the said terminal portion (206, 406);

- at least one transducer (13) located in the terminal portion of the containment wall (205) before the interrupted discharge portion (305) having regard to the direction of rotation of the rotor (1), said transducer (13) being adapted to detect and measure the centrifugal force exerted against it by the single article (10) being rotated; a logic unit (14) for processing the signal corresponding to the centrifugal force from the transducer (13) to obtain a value corresponding to the weight of the article.

10) An apparatus according to claim 9, in which the final portion (206) of the channel (106) is substantially horizontal, the transverse sl t (8) opens downwards and the separator blade element (11) is fixed to a supporting plate (4) which rotatably supports the rotor, said supporting plate (4) carrying also the peripheral containment wall (5) which presents, opposite to the said separator blade element (11), a portion (205) with an inner circumference having a diameter greater than the remaining portion (105) of the sa d containment wall.

11) An apparatus according to claim 9, in which the final portion (406) of the channel (306) is substantially vertical, the transverse slit (108) opens sidewards and the separator blade element (111) projects inwardly from the top of the containment wall (5) fixed to a supporting plate (4) which rotatably supports the rotor.

12) An apparatus according to claim 9 in which the separator blade element (11, 111) has a leading edge (1110) suitably chamfered.

13) An apparatus according to claim 12 in which the leading edge (1110) is provided with means for supplying a jet of air for facilitating the separation of the articles (10).