EP0594237B1 - Mixing device for materials with a high viscosity - Google Patents

Abstract

An appropriate device for mixing substances which have a high viscosity, comprising one or two mixing rollers (13) rotating about vertical axes, which can be raised and lowered into and out of a rotating cylindrical drum (3) with a vertical axis, containing the substances to be mixed, and which can be moved in radial direction, and driving means (5, 10, 15) for actuating the movements of the mixing rollers and of the drum so that the mixing rollers, which are first of all raised to make it possible to instal the drum (3) containing the substances to be mixed, enter the drum (3) in an approximately central position while being immersed into the substances to be mixed, and then they produce the mixing by the combined action of their own rotation and the rotation of the drum (3), while moving, during this operation, closer to the walls of the drum, so as to subject the substances to be mixed to crushing, rolling and drawing in all the regions of the drum (3); finally, the mixing rollers (13) again adopt a substantially central position and are raised out of the drum (3) to allow it to be moved away and at the same time are cleaned by cleaning devices (16).

Description

The present invention relates to a device suitable for carrying out the mixing of substances having a high viscosity. A particularly significant example, however not limiting, of substances for the mixture of which the device according to the invention is suitable, is represented by inks for offset printing, to which particular reference will be made in the following description.

For certain printing operations it is necessary to mix, in carefully proportioned proportions, inks of different colors. The metering of the inks for printing to be mixed is carried out by special devices, such as, in particular, that according to European patent application EP-A-0,538,926. After the different inks have been poured into the necessary proportions in a drum, they must be mixed in an extremely careful manner. This operation involves difficulties, particularly due to the high viscosity and the adhesiveness of the inks. According to the known technique, this operation is carried out by mixing devices making use of mixing members in the form of a butterfly, rotated in the mass of the inks to be mixed, or else by mixers of the type of kneading machines for bread making, or else still by other devices which, however, do not have a high efficiency in the operation and, after use, pose serious problems for their cleaning, which must be carried out by hand with considerable difficulty. Another problem with inks is that, upon contact with oxygen in the air, they are subject to oxidation and give rise to hardened films and persistent bubbles which then cause inconvenience. To this problem a solution is given, in certain cases, by enclosing the mixing devices and the drums in which the mixing is made in sealed envelopes in which a depression is caused, after which an inert gas, such as nitrogen, is introduced into it. But the conformation of known mixing devices is not in any way favorable to allow them to be enclosed in sealed envelopes, so that in many cases it is not possible to proceed in this way, and a subsequent operation of passing the substances mixed in a three-cylinder refiner, to expel the air that was incorporated during mixing.

These difficulties, which characteristically arise in the mixing of inks for printing different colors, or indeed a part of these difficulties, are also encountered in other cases of mixing of substances having high viscosity, as for example in the production of high viscosity inks, when it is necessary to disperse powder pigments in the varnish or in the varnishes.

Document FR-A-1.465.170 discloses a mixing device comprising: at least one mixing roller; means for supporting said mixing roller by allowing it to rotate about a vertical axis and to be raised and lowered in and out of a cylindrical drum containing the substances to be mixed, as well as to be moved in the radial direction in said cylindrical barrel; means for supporting said cylindrical barrel by allowing it to rotate about a vertical axis; and motor means for actuating said movements of the mixing roller and of the barrel; this assembly being arranged so that said mixing roller and said barrel are rotated; said mixing roller, first raised to allow the installation of the barrel containing the substances to be mixed, is lowered by entering the barrel in an approximately central position and by immersing in the substances to be mixed; then said mixing roller achieves mixing by the combined action of its own rotation and of the rotation of the barrel, moving during said operation towards the periphery, approaching the walls of the barrel, so as to subject the substances to be mixed to crushing , lamination and stretching in all regions of the barrel; finally the mixing roller again takes up a substantially central position and in this position it is lifted outside the barrel to allow its removal. This device corresponds to the preamble of claim 1.

One of the main aims of this invention is therefore to provide a mixing device capable of working with high efficiency, and consequently in relatively short times and reaching very complete degrees of mixing, also substances having high viscosity and adhesiveness, such than, in particular, inks for offset printing. Another object is to produce such a device which can be cleaned by simple operations and, at least in large part, capable of being mechanized. Another object is to produce such a device having such conformations that it does not pose serious problems for enclosing the functional parts in an environment out of contact with the atmosphere, in cases where such a requirement arises. Another object of the invention is to provide a device which works by its very nature in a way which tends to expel the air contained in the substances worked.

These objects are achieved, according to the present invention, by a device of the indicated type, characterized mainly in that it further comprises a cleaning device suitable for co-operating with said mixing roller during its extraction from the mixed substance, for detach from it at least most of the substance which remains adherent to said roller.

In this device the mixing operation takes place by a rolling and stretching action similar to that which, in a known manner, is carried out in three-cylinder machines for the production of viscous inks, with a high yield and obtaining a perfect mixture, in a relatively short time and with a relatively reduced energy consumption, as well as an effective action of expelling the air possibly contained in the substances worked. At the same time, the simple shape of the mixing members, constituted by one or more rollers, makes it possible to carry out the cleaning thereof according to the invention, at the end of the operation, simultaneously with their lifting, by means of simple cleaning devices, comprising a doctor blade or an air knife jet, arranged around the rollers, so that, when they reach their raised position, the rollers are already largely cleaned, on them remaining only a film or veil of takeaway stuff.

Preferably, the device also comprises a tank, disposed in the vicinity of the position provided for the barrel, containing a solvent or a detergent, in which the mixing roller can be lowered after the mixing operation. Said tank can also contain cleaning means, such as brushes or the like.

In this way it is possible to improve the cleaning of the roller, and the cleaning operations of the mixing members can be essentially mechanized, even if, if necessary, subsequent operations for complete cleaning, now in any case very light, can be carried out by hand.

In addition, the simple conformation of the mixing members and the possibility of supporting them on a supported plate, during the mixing operation, on the upper edge of the barrel containing the substances to be mixed, make it possible to establish, in a relatively easy manner. , the seal between said plate and the barrel, and therefore apply a vacuum inside thereof, and possibly introduce an inert gas.

In one embodiment, the device comprises a mixing roller only, which preferably has a diameter close to half the diameter of the barrel containing the substances to be mixed.

In one embodiment, the device further comprises a second mixing roller, parallel to the first roller and supported at a variable distance therefrom, and during the operation also the distance between the two mixing rollers is reduced, thus subjecting the substance to be mixed with lamination and stretching also in the region between the two mixing rollers.

The invention also relates to the mixing process carried out by the mixing device according to the invention.

• Fig. 1 est une vue en plan d'un dispositif mélangeur suivant l'invention, avec sa partie supérieure emportée en correspondance de la ligne I-I de la figure 2;
• Fig. 2 en montre une section verticale longitudinale faite suivant la ligne II-II de la figure 1;
• Fig. 3 en montre une section verticale transversale faite suivant la ligne III-III de la figure 1;
• Fig. 4 est une vue d'en bas de la partie centrale d'un fût susceptible de co-opérer avec le dispositif melangeur suivant l'invention; et
• Fig. 5 en montre une section faite suivant la ligne brisée V-V de la figure 4.

These characteristics and others, and other objects and advantages of the invention, will emerge more clearly from the following description of an embodiment, given by way of nonlimiting example, with reference to the accompanying drawings, wherein:

• Fig. 1 is a plan view of a mixing device according to the invention, with its upper part carried in correspondence with line II of FIG. 2;
• Fig. 2 shows a longitudinal vertical section taken along the line II-II of Figure 1;
• Fig. 3 shows a vertical cross section taken along line III-III of Figure 1;
• Fig. 4 is a view from below of the central part of a barrel capable of co-operating with the mixing device according to the invention; and
• Fig. 5 shows a section made along the broken line VV of FIG. 4.

The device according to the invention comprises a frame 1 provided with means, such as a roller belt 2, for handling the drums 3 containing the substances to be mixed. A rotating platform 4 actuated by a motor 5 by means of a transmission 6 is intended to support the barrel 3 during work, by putting it in rotation.

Above the mouth of the barrel 3, the frame 1 carries longitudinal guides 7 by which is supported a movable structure comprising a plate 8, intended to rest on the mouth of the barrel 3, and uprights 9, to the 'upper end of which is installed a motor unit 10. The latter is operatively connected to vertical screws 11 engaged in female screws of a console 12 which carries the mixing members and which, in this way, can be lifted up to the position shown by broken lines at 12 'in Figure 2, and can be lowered to the operative position, shown by continuous lines.

In the embodiment illustrated in the drawings, the organs mixers are two and they are constituted by two parallel rollers 13 of a relatively small diameter. However, as indicated by dotted and dashed lines in Figure 2, the pair of rollers 13 can also be replaced by a roller 13 'only. In this case, preferably, the single mixing roller has a relatively large diameter, for example half the inside diameter of the barrel 3. The following description refers to the embodiment comprising two mixing rollers 13, but it will be clear for the skilled in the art as the structures described must be simplified in the case where one uses a mixing roller 13 'only, and also as they must be supplemented in the case where one makes use of more than two mixing rollers .

Each mixing roller 13 is supported rotating by a carriage 14 which can be moved transversely on the support plate 12. The transverse movements of each carriage 14 are controlled by a motor means, not shown, which can be constituted by an electric motor or by a hydraulic or pneumatic cylinder, for moving the corresponding mixing roller 13 in a radial direction, relative to the barrel 3 and relative to the other mixing roller 13. On the carriages 14 are installed motor units 15 connected to the mixing rollers 13 for activate their working rotation.

Under the support plate 8 is mounted, around the mixing rollers 13, a cleaning means 16 (FIG. 2), constituted by a doctor blade and / or by a nozzle capable of blowing an air gap, for example according to the request of Italian patent No. TO 91 A 000791. Finally, near the working position of the barrel 3, and for example behind it (FIG. 2), is installed a washing tank 17 for the final cleaning of the rollers mixers.

The device described operates as follows. While the mixing rollers are in their raised position (from which the drawings show by broken lines only the console 12 'and the motor 15'), approximately centered with respect to the rotating platform 4, a barrel 3 containing the substances to be mixed is carried, along the roller conveyor 2, to the rotating platform 4, and this is rotated by means of the motor 5. If necessary, a seal is established between the support plate 8 and the mouth of the barrel 3, in order to be able to extract the oxygen and introduce an inert gas into the interior of the barrel 3. The mixing rollers 13, rotated by their respective motors 15, are then immersed in the barrel 3 and in the substances to be mixed, by lowering the console 12 by means of the motor 10 and the screws 11. The rollers 13, in their rotation, drag the substances to be mixed, due to their viscosity, and in the region interposed between the two rollers 13, this substance is subjected to lamination and drawing, which results in a particularly careful mixing. A similar action takes place between the mixing roller closer to the wall of the barrel 3, and the wall itself. In addition, during this operation, the mixing rollers 13 are moved, by means of the carriages 14, in a radial direction relative to the rotating barrel, so that any region of the substances to be mixed contained in the barrel is reached by the mixing action. , and the crushing, lamination and stretching action exerted between a mixing roller and the barrel wall increases as the distance between these two parts is reduced. This phenomenon is essential, in particular, in the case where use is made of a roller 13 only. When, on the contrary, use is made of two mixing rollers 13, the mutual distance between these rollers can be adjusted to a preferred value and kept constant, or else, and preferably, it too is reduced in time, by surrounding the rollers to make the action more intense as it continues. The radial movement of the mixing rollers can take place only once, or it can be repeated two or more times, periodically moving the rollers again towards the center.

When the mixing carried out is considered sufficient, the rollers 13 are again brought to a substantially central position, the rotation barrel 3 can be stopped and the mixing rollers 13 are removed from the now mixed substance, by lifting the console 12 by means of the motor 10 and the screws 11. During this lifting, one activates, for example by surrounding them with the mixing rollers , the cleaning means 16, which detach mixing rollers 13, which pass through them, most of the viscous substance which adheres thereto, by causing it to fall into the barrel 3. The central position of the rollers 13 during this phase of the operation gives assurance that the substances flowing from the rollers are collected by the drum 3 without contaminating the surrounding medium. The mixing rollers thus reach their raised position under a considerable, although not complete, cleaning condition.

While the barrel 3 already treated is taken away and a new barrel is carried on the platform 4, the support plate 8 with all the members which it supports is moved along the guides 7 until the mixing rollers 13 are placed on the tray 17 containing a solvent or a detergent and, where appropriate, cleaning means such as brushes or the like, and the mixer rollers 13 are lowered into this tray. In this way their cleaning can be carried, by mechanical means, to a considerable and possibly final degree; in any case, subsequent cleaning by hand, if necessary, becomes very easy. The rollers are then brought back to their initial position for a new working cycle.

The emptying of the mixed substance from the barrel 3 is usually carried out by inserting a piston 18 from the top into the barrel 3 (FIG. 5) and by opening an opening, constituted by a cylindrical hole, in the bottom of the barrel 3. However , during this operation the flow leaving through a simple hole in the barrel can easily incorporate or keep gas bubbles which then become harmful. In order to retain in the best way the effects of the careful work which the device according to the invention makes possible, an improved barrel can be used. An example of a barrel (not claimed) including an improvement is shown in Figures 4 and 5.

The bottom 19 of the improved barrel 3 has a wide opening below, which is normally closed by a flap 20, conical or flat, pushed by a spring 21. When pressure is exerted on the contents of the barrel by means of the piston 18, the force of the spring 21 is overcome and the valve 20 opens slightly, allowing the contents of the barrel to exit. The opening through which the viscous substance passes therefore has the form of a thin slit, and the high shear forces to which the viscous substance is subjected while passing through the slit cause the rupture of any gas bubble which may be present. . In this way the mixed substance, delivered in the form of a laminar jet, can be removed from the barrel in the best conditions for its use or for further processing, for example for making up.

Of course, the characteristics of the various viscous substances to be mixed, as well as their quantities, can be very variable, and as a function of these, the structure and operating parameters of the device according to the invention must be chosen in an appropriate manner. . Thus, the diameter of the mixing rollers must be chosen according to the diameter of the drums to be treated, the number of mixing rollers installed and the characteristics of the substances worked. The number of rollers used (one or more) depends either on the difficulties opposed to mixing by the substances to be treated, or on the working times available. The angular speeds and the directions of rotation (equal or opposite) of the barrel and of the mixing roller (s) can also vary to obtain the best results, and for this purpose it is advantageous that the motors actuating these parts are provided with suitable control means. .

Claims (11)

1. A device for mixing materials having a high viscosity, comprising; at least one mixing roller (13); means (7-12) for supporting said mixing roller (13) by allowing it to rotate around a vertical axis and to be raised and lowered into and out of a cylindrical drum (3) containing the materials to be mixed, as well as to be displaced in a radial direction within said cylindrical drum (3); means (4) for supporting said cylindrical drum by allowing it to rotate around a vertical axis; and motor means (5,10,15) for driving said movements of the mixing roller (13) and drum (3); the whole being so arranged that said mixing roller (13) and said drum (3) are put in rotation; said mixing roller (13), at first raised in order to allow installation of the drum (3) containing the materials to be mixed, is lowered by penetrating into the drum (3) in an about central position, and by plunging into the materials to be mixed; then said mixing roller (13) operates the mixing through the combined effects of its own rotation and of the rotation of drum (3), by displacing during said operation towards the periphery and approaching the walls of drum (3) in order to subject the materials to be mixed to squash, lamination and stretch in all the regions of drum (3); and finally the mixing roller (13) takes again a substantially central position and in this position is raised out of the drum (3) in order to allow removal thereof;
      characterized in that the device further comprises a cleaning device (16) suitable for cooperating with said mixing roller (13) when it is taken out of the mixed materials, in order to remove therefrom at least most of the materials remained adhering to said roller (13).
2. A mixing device as set forth in Claim 1, characterized in that it includes a tank (17), arranged near the operating position foreseen for the drum (3) and containing a solvent or a detergent, in which tank the mixing roller can be lowered after the mixing operation.
3. A mixing device as set forth in Claim 2, characterized in that said tank (16) also contains cleaning means, such as brushes or the like.
4. A mixing device as set forth in Claim 1, characterized in that it comprises a structure (1), a conveyor means (2) carried by said structure (1) for conveying the drums (3) containing the materials to be mixed, a turntable (4) for carrying the drum (3) being treated, a supporting plate (8) carried by the structure (1) and contacting the mouth of said drum (3), a shelf (12) suitable for being displaced in vertical direction under action of motor means (10,11) with respect to said supporting plate (8) and, installed on said shelf (12), at least one slide (14) carrying at least one mixing roller (13) and motor means (10,15) for driving said mixing roller (13) and for horizontally displacing said slide (14).
5. A mixing device as set forth in Claims 2 and 4, characterized in that it further includes means (7) for displacing said supporting plate (8) in a horizontal direction perpendicular to the displacement direction of said slide (14), towards and from said tank (17) containing a solvent or detergent.
6. A mixing device as set forth in Claim 4, characterized in that at least a part (10) of said motor means consists in electrical motors which drive control screws (11).
7. A mixing device as set forth in Claim 4, characterized in that some sealing means are arranged in order to operate between said supporting plate (8) and the mouth of drum (3).
8. A mixing device as set forth in any of the foregoing Claims, characterized in that, in an embodiment, it comprises a sole mixing roller (13'), whose diameter is preferably half the diameter of the drum (3) containing the materials to be mixed.
9. A mixing device as set forth in any of the Claims 1 to 7, characterized in that in an embodiment, it also comprises a second mixing roller (13), parallel to the first roller and supported at a variable distance therefrom.
10. A process for mixing materials having a high viscosity by means of a device comprising: at least one mixing roller (13); means (7-12) for supporting said mixing roller (13) by allowing it to rotate around a vertical axis and to be raised and lowered into and out of a cylindrical drum (3) containing the materials to be mixed, as well as to be displaced in a radial direction within said cylindrical drum (3); means (4) for supporting said cylindrical drum by allowing it to rotate around a vertical axis; and motor means (5,10,15) for driving said movements of the mixing roller (13) and drum (3); wherein said mixing roller (13) and said drum (3) are put in rotation; said mixing roller (13), at first raised in order to allow installation of the drum (3) containing the materials to be mixed, is lowered by penetrating into the drum (3) in an about central position, and by plunging into the materials to be mixed; then said mixing roller (13) operates the mixing through the combined effects of its own rotation and of the rotation of drum (3), by displacing during said operation towards the periphery and approaching the walls of drum (3) in order to subject the materials to be mixed to squash, lamination and stretch in all the regions of drum (3); and finally the mixing roller (13) takes again a substantially central position and in this position is raised out of the drum (3) in order to allow removal thereof;
       characterized in that said mixing roller (13) is cleaned by a cleaning device (16) when it is raised after each mixing operation.
11. A process as set forth in Claim 10, characterized in that said mixing roller (13) is further cleaned by plunging it into a tank (17) containing a solvent or a detergent and, in case, some cleaning means.

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