The subject of the present invention is a method for metering, in particular of liquids or fluids even of paste-like consistency.

Also a subject of the present invention is a device for the implementation of the aforesaid method.

The subject of the invention, as will be more easily understood from what follows, relates to the field of apparatuses for preparing mixtures, and in particular concerns pneumatic devices for metering paste-like liquids and fluids. That which is the subject of the present invention finds a use in particular, but obviously not exclusively, in pneumatic metering devices for fluid and/or paste- like base colours for producing coloured mixtures or compositions of all hues.

Apparatuses are known for metering paste-like liquids and fluids. In general, such metering apparatuses are provided with volumetric pumps connected to the supply reservoirs for the liquids and to the delivery nozzles; in order to deliver a predetermined quantity of liquid, the associated pump is actuated for a predetermined period of time, depending on the capacity of the pump.

Such apparatuses have a series of drawbacks and problems which are directly dependent on the metering system used.

If there are air bubbles or thickenings in the liquid, the quantity of liquid delivered is different from that desired, and in fact such air bubbles can alter the physical characteristics of the liquid (such as the weight or the specific volume), causing malfunctions, or the chemical characteristics of the liquid may change. In the case of distribution of liquids which harden on contact with air, these may dry in the pipes of the apparatus. In the case of liquids which are chemically sensitive to air (oxidation or the like) the liquid distributed may prove to be unsuitable for its intended use.

Because the delivery nozzles in general consist of short end pipes, in the case of rather paste-like liquids part of the liquid may remain in such nozzles or pipes, so that not only the quantity of liquid delivered varies, but, for example, owing to a long period of inactivity, the paste-like liquid may solidify, leading to malfunctions.

For the most part, it is necessary to meter several liquids into a single container. The distribution apparatuses for this purpose at present consist of a horizontal wheel on which are placed, in a circular arrangement, the reservoirs for the liquids and also the volumetric pumps with the respective nozzles. Beneath the said wheel there is placed, at the perimeter, a support surface for the container into which the various liquids are to be poured. The upper wheel with the reservoirs, pumps and nozzles rotates, from time to time bringing above the collecting container the nozzle relating to the liquid selected. Alternatively, similar apparatuses provide for the upper wheel, with reservoirs, pumps and nozzles, to be fixed and for the support surface for the collecting container to rotate, coming from time to time beneath the nozzles selected.

This type of apparatus requires a great deal of space, depending on the number of liquids to be metered, in particular when this occurs in the same container.

In order to remedy all the above drawbacks, a new type of apparatus has been designed and produced which avoids the phenomenon of thickening in the pipes, and that of clogging of the nozzles, and which delivers the necessary correct amount of liquids even in the presence of air bubbles.

Moreover, the exemplary embodiment considered concerns an apparatus which uses a single head for the delivery of a plurality of liquids, for each of which a device according to the invention is used. Such apparatuses have, in particular, minimum overall dimensions, however, contained within the limits imposed by the dimensions of the containers used at present.

In particular, all the metering nozzles are brought together in the aforesaid single head, with dimensions in plan which are smaller than the mouth of the container in which the liquids are to be received.

With the apparatus produced in accordance with the exemplary embodiment mentioned above and described in detail hereinafter, a solution has been provided in particular, in an advantageous manner, for the problem of compactness thereof, a feature which is certainly of advantage for the user with space problems. It is clear, however, that by the association, in a manner different from that under consideration, of a series of devices according to the invention, the apparatus finds a clearly industrial application even in the absence of the aforesaid problems of space and/or arrangement.

In the example being considered, the apparatus consists of several pumps for continuous circulation of the liquids, of a delivery head for the liquids which is provided with a number of delivery nozzles with pneumatic valves, equal to the number of base liquids to be metered, and of a support surface for the receiving container connected to a precision balance.

Each of the circulating pumps, one for each liquid, keeps the liquid in continuous circulation in the pipes, pushing the liquid from the supply reservoir towards the delivery nozzle, and from the platter, by means of a further recirculating pipe, the undelivered liquid is returned to the supply reservoir.

The nozzles each consist of a vertically sliding rod, the lower end of which slides in a chamber connected to the two pipes, one for the intake of the liquid coming from the pump and one which returns the liquid to the reservoir for that same liquid.

The lower end of the rod opens and closes the aperture from which the liquid is delivered, and at the same time the said rod partially closes and opens an aperture for the recirculating of the liquid to the supply reservoir. In the closed position in particular, the end of the rod protrudes slightly from the delivery aperture, so as to ensure that no liquid remains in the aforesaid aperture, while at the same time the liquid recirculating aperture is opened. In the open position, however, the end of the rod at least partially closes the aperture for the return or recirculating of the liquid to the reservoir while opening the delivery aperture so as to allow the emergence of the liquid itself.

The upper end of the rods is connected to suitable actuating means, preferably pneumatic, which control the vertical displacement of the rod itself.

In order to restrict the lateral dimensions of the head which contains the nozzles, rods, delivery apertures and actuating means, the rods themselves are of different lengths, so that the actuating means, of larger transverse dimensions than the rods, reach different heights and, in particular, alternately two different heights.

The new apparatus has considerable advantages both from the point of view of the accuracy of the liquid dispensed and as regards the overall dimensions of the whole of the nozzles.

When it is necessary to deliver a given quantity of liquid, the relative rod is raised, allowing the liquid to emerge; the balance connected to the support surface for the collecting container measures continuously the increase in weight and, on approaching the desired quantity of liquid, operates the occluding means in order to close the delivery aperture and to reopen it then at short intervals until the desired quantity is obtained.

When air bubbles are present in the liquid, these do not in practice affect the weight of liquid dispensed.

The delivery head for the liquids is very compact and can bring together in a small space, comparable with the mouth of the collecting container, a considerable number of liquid delivery nozzles; however, there are no rotating parts or movements to be carried out in order to align the collecting container and the delivery nozzles.

There is no possibility of the liquids solidifying or stagnating in the pipes in that the pumps, owing to the original configuration of the device according to the invention, are always operating and therefore maintain every liquid in constant, but slow, circulation.

A first subject of the present invention is therefore a method for metering liquid, particularly liquids of a paste-like consistency, wherein the liquid is conveyed by means of at least one connecting pipe and a pump from a supply station to a delivery station comprising at least one nozzle for delivery of the said liquid to a collecting station, characterized in that it comprises the following operating steps: a) the opening of the said delivery nozzle for a suitable time until a predetermined quantity by weight of liquid is obtained in the said collecting station; b) the emission from the said collecting station and conveying to the delivery station of an operating signal measuring the quantity by weight of liquid referred to in step a) in order to effect the closure of the said delivery nozzle; c) the opening, on receiving the said operating signal, and simultaneously with the closure of the delivery nozzle, of the circuit for recirculating the liquid to the supply station.

A further subject of the present invention is a device for metering, particularly of a liquid of paste- like consistency, comprising a supply station for the said liquid and means, preferably in the form of a pump, for conveying the said liquid to a delivery station for the latter, comprising a delivery nozzle, characterized in that the said means for conveying the said liquid to the delivery station are operating constantly and the said delivery station comprises a recirculating chamber capable of delivering the said liquid or fluid to the collecting station through the said delivery nozzle, or to the supply station through a recirculating pipe into which the said liquid is brought when the said delivery nozzle is closed.

The accompanying figures show, by way of a non-limitative example, an embodiment of the invention for implementation, in compact form and in the case where the liquids are base colours.

More precisely, in the aforesaid figures: Figure 1 is a block diagram illustrating a delivery station for the liquid in the step of delivery of the latter, in an apparatus using a series of devices according to the invention; Figure 2 is a block diagram analogous to that in Figure 1 which shows the delivery station in the step of recirculating of the liquid; Figure 3 is a diagrammatic view of a delivery and recirculating head according to section ffi-ffi in Figure 4 in the said apparatus using a series of devices according to the invention; Figure 4 illustrates the head from Figure 3 according to section IV-IV of the same Figure.

Referring firstly to Figures 3 and 4, a description will now be given, by way of example, of an apparatus for metering liquids, in the compact version as specified above.

The apparatus comprises a delivery head which incorporates a series of devices according to the invention, one of which is indicated in the assembly by E in Figures 1 to 3, while two of the remainder, shown by dashed lines, are designated by the references E' and E' in Figures 1 and 2.

The delivery head consists principally of three superposed frame parts or components 1, 2, 3.

In the lower part 1, connections 5 are provided for the feeding or supply of the liquid and nozzles or connections 4 for the recirculating or return flow of the latter respectively from and towards a supply station indicated by S in Figures 1 and 2, while S' and S" (shown by dashed lines) indicate two of the remaining supply stations. The number of such pairs of connections may, for example (as shown), be sixteen, where a base colour circulates for each pair of connections. Such connections 4, 5 communicate with a recirculating chamber 11 of the station E, in the lower part of which a suitable delivery nozzle or aperture 7 is provided through which the liquid is dispensed.

Inside the recirculating chamber 11 can slide the rod 6 of a pneumatic actuating means, the lower end 8 of which, in the closed position, occludes the liquid delivery aperture 7. In particular, the said rod 6 has an enlarged portion 6' for the opening and closing of the nozzles 4, 5.

In the open position, the rod 6 opens the supply connection 5 and the aperture 7, at the same time closing the recirculating pipe 4 (left-hand piston in Figure 3), while in the closed position it closes the connection 5 and the aperture 7 while it opens the recirculating pipe 4 (right-hand piston in Figure 3).

The two upper parts 2, 3 of the head receive inside them the actuating means for the rods 6; in this example, the actuating means consist of pneumatic pistons 9 that can slide inside suitable cylindrical seats 12 into which or out of which compressed air is conveyed through suitable pipes 10.

In particular, the pneumatic pistons 9 are housed alternately in the intermediate part 2 and in the upper part 3 of the head so as to limit the lateral dimensions of the whole of the liquid metering nozzles.

In the case illustrated, a delivery head is shown with sixteen metering components which are distributed in an area smaller than the aperture of a suitable receiving container indicated by R in Figures 1 and 2. In the exemplary embodiment under consideration, that is to say, in the compact version of the apparatus, the said container R is the only one, as specified above, but it is obvious that others could be provided, particularly for use on an industrial scale, the number depending on the specific requirements and applications.

The solution under consideration has considerable advantages insofar as the constituents to be metered are delivered directly into the receiving container R placed beneath the relative head.

According to one of the characteristics of the present invention, the said receiving container R is arranged on a balance, indicated by B in Figures 1 and 2, to measure the quantity by weight of liquid introduced into the said receiving container R.

According to a further characteristic of the invention, the balance B is arranged, in any known manner, to emit a continuous operating signal for reading the quantity by weight of liquid. The signal, as can be seen in particular in Figures 1 and 2, arrives at a separate unit comprising, for example, a computerized comparison and monitoring device indicated generally by B', which in turn sends a command to the actuating means of one of the devices E so that the latter switches from the state in Figure 1 (delivery of liquid) to that in Figure 2 (interruption of the delivery).

The two states are shown diagrammatically by the symbols of valve open (Fig. 1) and valve closed (Fig. 2).

According to another advantageous characteristic of the invention, the said operating signal, suitably processed and computerized, is such as to operate, shortly before the aforesaid quantity by weight of liquid is reached in the receiving container R, the cyclic or pulsed opening and closing of the delivery nozzle 7 with a suitable frequency so as to obtain delivery of reduced doses of liquid which makes it possible to reach, in a gradual and precise manner, the total quantity desired.

In the case of metering of small quantities of liquid, such pulsed opening and closing of the delivery nozzle occurs for the whole duration of the metering operation.

Finally, it should be noted that such pulsed opening and closing also has an induced effect of cleaning the delivery nozzle.

As already indicated, the invention finds an application in all situations concerning the metering of one or more liquids, especially when of paste-like consistency or of reduced fluidity, ensuring not only precision of metering but also the substantial elimination of the problems and drawbacks of the known systems.

The characteristics and advantages of the method and the device according to the present invention are revealed by the description given above.

Finally, it is clear that conceptually or structurally equivalent variants and/or modifications may be applied to the aforesaid method and device without thereby departing from their scope of protection.