EP0298407A2

EP0298407A2 - Process and apparatus for the net weight dosage of liquids

Info

Publication number: EP0298407A2
Application number: EP88110646A
Authority: EP
Inventors: Tommaso Mori Checcucci
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-07-08
Filing date: 1988-07-04
Publication date: 1989-01-11
Also published as: IT1213641B; EP0298407A3; JPS6470398A; IT8703546A0

Abstract

The process provides the transfer of the container to be filled in succession below a plurality of feed stations (13a-13d) having a progressively smaller flow rate and alternatively thereto onto the same number of check balances (7a-7d) so as to obtain, in successive steps, the precise refinement of the dosage. All of the balances (7a-7d) being correlated to electronic processors which adjust the partial dosages and check the final results. The invention also relates to an apparatus for the execution of said process.

Description

The present invention relates to a process and to an apparatus for the net weight dosage of liquids.
In the field of weight dosage machines, the concept of volumetric solid product dosage, divided among a succession of stations for the filling and subsequent checking on a balance with the progressively decreasing and corrective addition of portions of product, is already known.
This concept is included, for example, in the German patent No. 2216143 to obviate variations in specific weight. This concept, however, is not applicable to the dosage of liquids due to the slowness which the process would acquire. In fact while any volume of solid product can be suddenly unloaded from the hopper into the volumetric dosage machine and from there into the container (bag or box), on the contrary the transfer of a liquid into its final container (bottle, flask, can) is always very slow since it must occur through a narrow opening which indeed characterizes such containers.
The aim of the present invention is to provide a process for the net weight dosage of liquids which allows to apply the concept of net weight dosage by means of successive corrective feeds even in the case of liquids.
This aim is achieved by a process which is characterized in that it comprises the conveyance of the containers through successive feed stations alternated with weighing stations, the feeding, at each feed station, of an additional dose with decreasing weight with respect to that of the preceding feed station, according to the weight check performed in the preceding weighing station, and in that in the final station an additive or subtractive corrective feed is performed depending on whether the weight of the dose is below or in excess of its nominal value.
Within the scope of this aim, an object of the invention is to provide an apparatus for carrying out said process which is characterized in that it comprises a line composed of a first weighing station for the detection of the empty weight of the containers, at least one first feed station wherein the feed of a first dose of liquid is effected, a second weighing station for the detection of the first fed dose, a further feed station for the addition of a further dose of product depending on the weight of the dose detected in the second weighing station, a third weighing station for detecting the overall weight of the doses fed in the preceding stations, a final station adapted to feed or draw liquid if the sum of the doses fed in the preceding stations is below or in excess of a nominal value, means for intermittently advancing said containers through said feed and weighing stations and said final station, with a pitch equal to the distance between said stations.
An example of the invention is illustrated in the accompanying drawings, wherein:

figure 1 is a schematic plan view of the apparatus which executes the process;
figure 2 is a lateral view thereof;
figure 3 is a sectional view of the feed unit of the final station; and
figure 4 is a plan view of an apparatus according to another aspect of the invention.

With reference to figures 1 and 2, the apparatus comprises a conveyor 1, actuated in the direction of the arrow A, for the conveyance of empty containers 2 guided to form a line which stops against an abutment.
At the end of the conveyor 1 there is a pusher 4, e.g. of the pneumatic type, which pushes the individual containers onto a sliding plane generally indicated at 5, along which weighing stations and stations for feeding the liquid to be metered are arranged. The sliding plane 5 is actually constituted by the plates 6a-d of balances 7a-d and by planes 8a-d co-planar with the plates 6a-d and interposed therebetween so as to act as bridges during the transfer of the containers 2.
The advancement of the containers along the sliding plane 5 is effected by means of a pair of horizontal parallel chains 9 connected to one another by transverse bars 10 having the function of traction elements.
The chains 9 are closed in a loop around respective pairs of toothed spindles 11, 12 and their upper portions move in direction B at a level overlying the plane 5 so as to act rearwardly on the containers 2 transferred thereon.
The spindles 12 are motorized by a motor reducer of the step motor type (not illustrated), programmed for an advancement by a step P followed by a small backward movement P1 which has the purpose of spacing the traction bars 10 from their respective containers. It should be noted that at each step the containers which are on the sliding plane 5 pass from the plates 6a-c of the balances 7a-c onto the planes 8a, 8c, 8d and from the planes 8b-d to the plates 6b-d.
The translatory speed of the bars 10 is variable with constant acceleration for the first portion of the step P and with constant deceleration for the second portion of the step P so as to reduce the disturbance of the contents in particular in the case of liquids and to stabilize the container.
A plurality of feed units 13a-d is provided for the filling of the containers and each is mounted on a support 14 supported by columns 15 which rise substantially vertically from a base 16. The feed units 13a-d, which constitute the feed stations together with the planes 8a-d, receive the product from a common hopper 17 and feed increasingly finer doses in direction B. The last feed unit 13d is conveniently preset for a fine adjustment of the dose and is expediently constituted (see figure 4) by two coaxial tubes 18, 19 the outer one 18 whereof is connected to a vacuum tank 20 which collects the small amounts poured in excess through a tubular branch-off 21. An opening 22 is provided along the branch-off 21 and is controlled by a shutter 23 actuated by an electromagnet 24. The inner tube 14 is connected to the hopper 17 and is controlled by a mushroom-shaped shutter 25 adapted to close the outlet of the inner tube 19. The shutter 25 is associated, by means of a stem 26 coaxial to the tube 19, with a ferromagnetic core 27 controlled by an electromagnet 28 which can thus actuate the opening and the closure of the shutter.
The feed units 13a-d are adapted to be raised and lowered with respect to the containers 2. In particular the lower ends of the tubes 18, 19 of the feed unit 13 are adapted for immersion into the liquid so as to not only add the final dose but also to correct any excess. In fact in case of excess of liquid in the container the shutter 23 is actuated to its position of disengagement from the opening 22, allowing the duct 29 defined between the tubes 18 and 19 to communicate with the vacuum tank 20 and therefore allowing the excess liquid in the container to be aspirated in the required amount into the tank 20.
Vice versa, in the case of an excessively low dose in the container, the shutter 23 is actuated in its position of cutoff of the opening 22 while the shutter 25 is actuated until the required dose is obtained.
The containers 2, once they are filled, arrive at a removal conveyor 30 actuated at constant speed, laterally whereto a pneumatic-cylinder expeller 31 is installed for the possible expulsion of non-standard containers.
The operation of the described apparatus is as follows. The containers 2 arriving from the conveyor 1 are transferred onto the plate 6a of the first balance 7a where the weight of the empty container is determined by static weighing, i.e. with the object motionless on the plate and free from any retention or contact as an effect of the backward motion P1 of the transverse bar 10.
The successive step comprises the translatory motion of the empty container on the sliding plane 5 up to the first feed station, where it is positioned on the plane 8a. The feed unit 13a delivers an amount of liquid which is less than half of its capacity. Then the container thus partially filled is transferred to the successive station 13b, 8b where it again receives an equal amount of liquid and then passes to the successive weighing station 6b, 7b where the balance 7b determines the weight of the liquid poured by the two first feed units 13a, 13b and, as a difference with respect to the desired net weight, the amount which is still to be poured. This amount is indeed poured when the container, at the successive step, reaches the station 8c, 13c below the feed unit 13c. The possible positive or negative difference in weight is determined when the container reaches, with the successive step, the balance 7c.
The filling process is completed with the precision feed unit 13d which can not only pour but, in the case of an excess of poured product, can aspirate until the nominal weight is reached. Finally the exactness of the weight is checked with the last balance 7d.
In the illustrated apparatus it is assumed that the delivery occurs via feed units the flow rate whereof decreases in direction B. Once the flow rates of the feed units are set, the amounts poured at the various stations are functions of the viscosity of the product in the feed duct at the pressure and temperature preset and stabilized in the hopper and of the duration of said feed, i.e. of the pressure, of the temperature and of the time.
The maximum pressure is that which creates no problems of bouncing on the bottom of the container or dangerous disturbances on the free liquid surface of the prefilled container.
When starting the apparatus with an unknown product, an automatic calibration is performed as follows: after resting a single container on the balance 7a, the apparatus is started which, after having weighed the container, transfers it below the feed unit 13a which is preset, in this initial setup or calibrated configuration, to deliver the product for a unitary time.
The other feed units 13b-13d are inhibited by respective so-called "no can-no fill" devices 32a-32d. The balance 7b subsequently weighs the product metered by 13a-b in the time unit, thus determining the sum of the actual flow rates of the feed units 13a, 13b.
In the successive feed station the feed unit 13c delivers product for the time unit. The balance 7c, measuring the additional liquid, determines the real flow rate of the feed unit 13c. The container finally exits from the apparatus and is removed as it is only partially filled.
At this point the setting of the flow rates of the feed units is complete and by means of a computer it is possible to determine the duration of the delivery of the feed units 13a, 13b so that in approximately the same time the feed unit 13c pours the amount complementary to the obtainment of the preset nominal weight.
The exactness of the calculation is confirmed or denied by the balance 7c. In fact the delivery supplied by the feed unit 13c should always remain positive and have a duration which does not exceed that of the two preceding feed units.
Thus, once the calibration is performed with a single container, to be expelled once the operation is complete, actual production may commence immediately. During the continuous process the balance 7d supplies information regarding the final errors, which is used with a process of the so-called feedback type to optimize the deliveries of the feed units 13a-13b.
The optimum operating condition is thus stored so that the described setup is no longer required; in the future it will be sufficient to recall the product's code.
Small pressure or temperature variations in the hopper determine systematic errors which are minimized during the process, as already described.
The four balances 7a-7d send their weight signals, as already imaginable, to a single electronic computer having microprocessors and memories which operates according to a program which is illustrated herein in its essential features. The correlation of the four balances implies the fact that the zero value is assumed for them all when their plates are unloaded and so is a value of comparison with a product weight required by law which is proximate to the declared capacity of the balance.
The checking of the zero value assumed each time the plate of the balance is unloaded is entirely automatic.
The machine as described above has a longitudinal modularity which consists of a succession of modules, each constituted by one or more filling and feed stations, all equal in length to the step P, which allow the obtainment of greater precision in weighing or greater operating speed by means of the addition of other filling and weighing stations. The modularity may also extend transversely, thus creating a battery of parallel lines 33a-33g as illustrated in figure 4, each whereof is constituted by a sliding plane similar to the one of figure 2, composed of a succession of planes and balances.
The feeding of the apparatus is provided by means of a feeder conveyor 34 on which an auger 35 is arranged. The first portion of the auger has a progressively increasing pitch, while the second portion has a pitch C which is equal to that of the axes of the balances of each line. The auger 35 dispenses, upstream, an accumulation of containers in mutual contact which is sufficient to ensure not only the continuous feed of the auger's initial thread but also the successive feeding of all the lines. The auger is actuated by a step motor reducer 36 programmed to perform, at each cycle, a number of turns equal to the number of lines of the apparatus.
The auger starts to rotate during the filling-weighing steps and stops when it has made such a number of turns as to ensure the arrangement of all the containers facing their respective lines.
The containers are guided on both sides by the fixed but adjustable guides 37 and by the vertically movable guide 38 which retracts downwards when the pusher 39, constituted by a horizontal blade which enters the space existing between the auger 35 and the conveyor plane 34 and actuated by a pneumatic cylinder 40, advances, at the end of each operating cycle, and pushes the containers into the first station, now constituted by a battery of balances preset to weigh them when empty. The advancement from the first station to the successive ones is obtained with advancement bars of the type previously indicated by the reference numeral 10 carried by a pair of lateral chains similarly to what has already been described with reference to figures 1 and 2.
At the end of the filling and checking operations the containers are aligned in a number equal to the number of lines 33a-33g on which they have been distributed, and are transferred onto an output conveyor 41 parallel to the conveyor 34.
The conveyor 41 is advanced by means of a motor reducer 42 actuated at variable speed so as to ensure the maximum stability of the containers. The direction of advancement of the conveyor 41 may be the same as that of the conveyor 34 or the opposite one.
A substantial advantage of the invention resides in the reduced dimensions of the apparatus, performance being equal, which is to be ascribed to the very limited presence of idle areas. Other advantages are the extreme ease with which it is possible to change the format, for which only the replacement of the feeding auger 35 is required.
The invention is susceptible to numerous modifications and variations. For example, instead of a weighing and filling station it is possible to provide two or more stations for the simultaneous filling of two or more containers, so as to increase the operating capacity of the apparatus.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

1. Process for the net weight dosage of liquids in containers, characterized in that it comprises the transfer of the containers (2) through successive feed stations (13a-13d) alternated with weighing stations (7a-7d), the feed at each feed station (13a-13d) of an additional dose decreasing in weight with respect to that of the preceding feed station according to the weight check performed in the preceding weighing station (7a-7d), and in that in the last feed station (13d) a corrective additive or subtractive feed is performed depending on whether the weight of the dose is below or in excess of the nominal value.

2. Process according to claim 1, characterized in that it comprises the transfer of the containers (2) through a first weighing station (7a) for the detection of the empty weight of the containers, then through at least one first feed station (13a) whereat the feed of a first incomplete dose of liquid is effected, a second weighing station (7b) for detecting the metered dose, a further feed station (13c) for the addition of an additional incomplete dose of liquid in relation to the weight of the dose detected at the second weighing station (7b), a third weighing station (7c) for detecting the overall weight of the doses fed in the preceding feed stations (13a-13c), a final station (13d) adapted to meter or draw some liquid if the sum of the doses fed in the preceding stations is below or in excess of a nominal value.

3. Process according to claim 2, characterized in that the containers (2), before the second weighing station (7b), are conveyed to a further feed station (13b) successive to said first feed station (13a).

4. Apparatus for the net weight dosage of liquids in containers, characterized in that it comprises a line composed of a first weighing station (7a) for detecting the empty weight of the containers, at least one first feed station (13a) in which the feeding of a first dose of liquid is performed, a second weighing station (7b) for detecting the first fed dose, a further feed station (13c) for the addition of a further dose of product in relation to the weight of the dose detected in the second weighing station (7b), a third weighing station (7c) for detecting the overall weight of the doses fed in the preceding stations, a final station (13d) adapted to feed or draw liquid if the sum of the doses fed in the preceding stations is below or in excess of a nominal value, means (9, 10) for intermittently advancing said containers through said feed and weighing stations and said final station with a pitch (P) equal to the distance occurring between said stations.

5. Apparatus according to claim 4, characterized in that said final station (13d) comprises a pair of vertical coaxial tubes (18, 19) the inner one (19) whereof is connected to a hopper (17) for containment of the liquid and has its outlet controlled by a shutter (25) actuated by an electromagnet (28), said inner tube (19) defining with said outer tube (18) an annular duct (29) connected to a vacuum tank (20) through a tubular branch-off (21) controlled by a shutter (23) actuated by an electromagnet (24).

6. Apparatus according to claim 4, characterized in that it comprises a plurality of parallel lines (33a-33g) fed with containers (2) by an auger (35), said auger having a portion equal in pitch (C) to the distance between the lines, pusher means (39, 40) being provided for the transfer of the containers onto said lines.