Such systems are generally known in the prior art. For dosed release of for instance colouring agent as additive, use is normally made of weighing means in order to determine the weight of at least the additive in a container and to regulate the dosage on the basis of a measured weight and the change thereof through time.

Such systems with weighing means have the characteristic that limited amounts of additive can be kept in containers of different dispensing means in order to be able to determine precise weight variations within a weight range using the weighing means, for the purpose of a proper dosage. This entails the containers also having to be replenished after a time. This replenishing usually takes place manually and the replenished quantity of the additive is therefore not usually known exactly.

The starting situation, and more particularly the starting weight of the additive after replenishment is thus not known, or not precisely. This has an adverse effect on the dispensing means in achieving a desired accuracy, particularly after replenishing of a container.

Furthermore, the replenishing is normally carried out manually, which is a drawback, particularly in a production environment where volume and throughput speeds associated with an automated system are relevant, wherein manual replenishment is undesirable and stands in the way of high production speeds.

The present invention has for its object to improve the art, whereby the stated drawbacks of the known art can be obviated or at least considerably reduced, for which purpose a system according to the invention is distinguished by the measures in the definition of claim 1.

In such a system diverse feeds for additives are used via a single replenishing container in order to enable replenishment of the additives in the containers. Full automation can thus be achieved, quantities of additives for replenishing can be precisely determined for each of the containers, and a single replenishing system can in fact suffice for all the dispensing systems.

A system according to the invention preferably has the features of claim 2. The replenishing chamber in the form of a vacuum chamber herein draws in a quantity of additive, which is preferably determined properly and accurately beforehand, from a relevant feed in order to provide this quantity of additive only to the throughfeed means associated with the dispensing means requiring replenishment of additive. Thus is ensured that the additive from a feed finds its way only to the dispensing means requiring replenishment.

A system according to the invention further preferably has the properties of claim 3. Use can herein be made in favourable manner of the weighing means which are already applied for dispensing in the case of systems where dispensing takes place on the basis of weight changes. Such an embodiment then provides a simple and elegant realization of all the desired functions, but also when dispensing takes place on the basis of any other principle.

A system according to the invention can also have the features of claim 4. The valve means in the chutes to the containers can be actuated in appropriate manner by a control in order to provide a relevant container, which actually

requires replenishment, with the necessary replenishment.

A system according to the invention can further be provided with the features of claim 5. This is a particularly favourable embodiment, wherein automated and optimal dispensing characteristics are provided. Recycled material can also be processed in suitable manner with such an embodiment. It is precisely for this reason that the invention also comprises a system with the features of claim 6 which is independent of claim 1, which system can also have several of the features already stated above in diverse preferred embodiments of the invention according to claim 6.

The invention will be further elucidated hereinbelow with reference to the annexed drawings, in which fig. 1 and fig. 2 show an embodiment of a system according to the invention in diverse operating states thereof.

In the figures is shown a system 1 for dosed addition to a main flow 2 of selectively at least one of at least two additives. The system comprises two dispensing systems 3,4 for two additives, which have in each dispensing system 3,4 a container 5,6 for the relevant additives and a controlled adding mechanism 7,8. The adding mechanisms 7,8 ensure controlled discharge to main flow 2 of the relevant additive, addition of which to the main flow is desired at a determined moment. The additives can be colouring agents or material for recycling. One colouring agent at a time can herein be selected, but it is also possible to provide colour mixing by combined feeding to the main flow of different colouring agents or material for recycling.

Dispensing means 3,4 each comprise separate weighing means, in the form of load cell 9, which determine the weight of at least the additive in each of the containers 5,6. The decrease in the weight of the additive resulting from dispensing and sending the additive to main flow 2 can thus

be determined, and the rate thereof can be regulated with a control (not shown) which acts on the adding mechanisms 7,8.

These adding mechanisms 7, 8 can comprise a worm screw 10 which is driven by for instance a stepping motor (not shown), which in turn is under the influence of the control.

If the main flow 2 is running at the position indicated in the figures, it may be useful to arrange plates 20 over the worm screws 10 of dispensing system 3,4 protruding into a passage 19, particularly if the load cell 9 of each dispensing system 3,4 also supports the worm screw 10 and the quantity of material therein is also included in the measurement of the weight for a more reliable and accurate weight measurement. The main flow 2 does not then exert any pressure on worm screws 10, which would be expressed by influencing the weight measurement by load cell 9.

If the weight of the additive in a container 3,4 decreases while an associated adding mechanism 7,8 is in operation, a situation will occur after a time where replenishing of container 3,4 is desired. This is also determined by the weighing means or load cell 9, which provides a signal to this effect to the control. The control can also be adapted to itself determine from a signal from load cell 9 that a quantity of additive smaller than a threshold value is present in container 3,4, in order to set filling means 11 into operation on the basis of this' determination.

Filling means 11 comprise a number of (here two) feeds 12,13 for each of the additives. The feeds are connected to a common replenishing container in the form of vacuum chamber 14. An underpressure can be applied to vacuum chamber 14, wherein a connection is then left to only one of the feeds 12,13 in order to carry additive from the relevant feed 12 or 13 into vacuum chamber 14. Use can be made for this

purpose of valves (not shown) in each of the feeds 12,13, or of other random components to hold open only one of the feeds 12 or 13. The replenishing chamber can thus be provided with the desired additive required to replenish a relevant container 5,6. It is possible here to carry a properly measured quantity of additive for replenishing into the replenishing container when the replenishing container is for instance placed on scales or at or on any other random weighing means, or when the feed capacity is well known and the feed of additive for replenishing is sustained for a well-defined or known time. Within the scope of the present invention the replenishing container 14 can thus take a form very different from a vacuum chamber, for instance a simple container which only collects additive, wherein the feeds can then be equipped with means for carrying a known quantity of additive into the container, such as their own worm screw (not shown). All these types of possibilities within the scope of the invention for carrying additive into the replenishing container are designated as infeed means.

The replenishing container can also be provided with a cleaning system, particularly for the purpose of preventing contamination of later batches of additive for replenishing by residues of previous batches. This can usually be attributed to incomplete throughfeed of additive substance out of replenishing chamber 14, in particular when the additive is material for recycling which has been ground. For this purpose such a cleaning system comprises for instance pneumatic lines 21 with blow nozzles 22, fed by an air pressure pump. A filter 24 can be arranged in replenishing chamber 14 to prevent such material entering the environment.

The system further comprises between vacuum chamber 14 and containers 5,6 of dispensing systems 3,4 two chutes 16 which form part of throughfeed means 15 for transporting

additive from vacuum chamber 14 to containers 5,6. Chutes 16 form an inverse Y-shaped channel, with selection means in the form of a valve 17 in the bifurcation. Valve 17 can be placed in one of two positions by the control (not shown). These two positions are shown in figures 1 and 2. In the position of valve 17 container 5 of the dispensing system 3 on the left in the figures can be replenished, and in the position of figure 2 the right-hand container 6 can be replenished. The control provides for setting of valve 17 in one of the two shown positions, which corresponds with which of the two containers 5 or 6 must be replenished, and which additive is carried into vacuum chamber 14 from feeds 12,13.

The system further comprises determining means in the form of a sensor 18 for determining the need for additive.

Sensor 18 is herein arranged in a passage 19 for main flow 2.

It is thus possible to determine which materials make up the main flow 2. There may in fact be no need for additive in the case that material from the main flow, to which additive has already been added, is recycled. If additive has already been added to such recycled material of main flow 2, there is no need to add additive again when this material for recycling is introduced into the main flow instead of material for the main flow without additive already added thereto. The sensor is connected for this purpose to the control (not shown), which can act on the adding mechanism 7,8 in order to render it (temporarily) inoperative in such a case as long as recycled main flow material with already added additive is passing through passage 19.

In the embodiment shown in the figures it is however recommended that a container 5 or 6 of the shown dispensing systems 3,4 serves to contain material for recycling. The material for recycling is then basic material from the main flow, to which additive such as colouring agent is added and

which is processed using for instance an injection moulding apparatus or an extrusion plant. Residues usually occur here, such as edges, injection moulding gate fillings and the like to be severed, broken or otherwise removed from the products made using such production apparatus. These are recycled as follows. After being released from the end products, the residues are ground and re-used by providing them to replenishing chamber 14 via one of the feeds 12,13.

The material for recycling can thus be added in dosed manner as one of the additives to a main flow 2, to which no additive at all has yet been added prior thereto. Sensor 18 can then be omitted and be functionally replaced by the load cell of the relevant container 5 or 6 with the material for recycling, when this load cell 9 of the relevant dispensing system for adding the material for recycling as additive is used to determine the quantity of material for recycling therein, and the control is able to adjust the rate of the addition of material for recycling to the quantity of the material for recycling available in these relevant containers 5,6. Here the control will otherwise also adjust thereto the rate of addition of the other additives, such as colouring agents, since less colouring agent will need be added due to the addition of material for recycling. The composition of additives for the main flow can thus be adjusted in particular to quantities of the material for recycling that become available. It is thus also possible to take into account the rate at which the quantities of material for recycling become available, for instance from a grinding apparatus for grinding the above described residues. If this were not taken into account, the quantity of material for recycling available in container 5 or 6 can be suddenly exhausted, whereby an abrupt change in the composition is necessary, which could result in disruption of the system.

Precisely by taking this into account, such disruption can be prevented or avoided.

The present invention is described in the foregoing with reference to the accompanying drawings. Diverse additional and alternative systems will now occur to the skilled person, all of which must however be deemed as embodiments of the present invention to the extent that they fall within the scope of protection defined by the appended claims. Sensor 18 is thus only given by way of example, since it is also possible for an automated system to inform the control that recycled material will be processed at any moment, so that the requirement for a sensor, which can be a colour sensor, may become unnecessary, or the sensor need only be used for the purpose of verification. Other embodiments have already been considered in the above discussion of the diverse components of the system in the accompanying figures. The control can further form part of the control of an entire installation, of which a system according to the invention only forms a part. The replenishing container does not have to be a chamber but can comprise a passage or conduit, as long as a selection from diverse sources and destinations of additive can be realized herein, so that a need for diverse replenishing systems, separately for each dispensing system, can be avoided. The main flow can also run outside the configurations shown in the figures, wherein a coupling 25 serves to connect the dispensing devices to a separate passage for the main flow. Nor is the invention limited to two dispensing systems, and the figures even show that a third worm screw 10 of a further dispensing system debouches in passage 19, where at least the additives are brought together, possibly also with main flow 2.