EP0594237A2 - 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 in no 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.

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 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 it to be moved away.

Preferably, 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. also for lamination and stretching in the region between the two mixing rollers.

Due to these characteristics, the mixing operation does not take place by simple displacement of moving parts in the mass of the substance to be mixed, as in known devices, but by a lamination and stretching action similar to that which , in a known manner, is carried out in three-cylinder machines for the production of viscous inks, and therefore with a particularly high yield. At this high efficiency it follows that a particularly perfect mixture is achieved, in a relatively short time and by a relatively reduced energy consumption, as well as an effective action of expelling the air possibly contained in the worked substances .

Preferably, the device further comprises a cleaning device suitable for co-operating with said mixing roller during its extraction from the mixed substance, to detach from it at least most of the substance which remains adherent to said roller.

In this way, the extremely simple shape of the mixing members, constituted by one or more rollers, makes it possible to carry out cleaning thereof, at the end of the operation, simultaneously with their lifting, by means of simple cleaning devices, comprising a doctor blade or else 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 substance to take away.

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.

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

An object of the invention is also to perfect a barrel intended to be treated in a mixing device, to perform in the best conditions the extraction of the barrel of the mixed substance.

• 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 perfectionné pour co-opérer avec le dispositif melangeur suivant l'invention;
• 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 an improved barrel for co-operating with the mixing device according to the invention;
• 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 main illustrated embodiment, 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. With the aim of retaining in the best possible way the effects of the careful work which the device according to the invention makes possible, the invention also provides an improvement to the means for discharging the barrel of the mixed substance. This 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 taken 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 (15)

Device for mixing substances having a high viscosity, characterized in that it comprises: at least one mixing roller (13); means (7-12) for supporting said mixing roller (13) allowing it to rotate about a vertical axis and to be raised and lowered in and out of a cylindrical drum (3) containing the substances to be mixed , as well as being moved in the radial direction in said cylindrical barrel (3); means (4) for supporting said cylindrical barrel by allowing it to rotate about a vertical axis; and motor means (5,10,15) for actuating said movements of the mixing roller (13) and of the barrel (3); this assembly being arranged so that said mixing roller (13) and said barrel (3) are rotated; said mixing roller (13), first raised to allow the installation of the barrel (3) containing the substances to be mixed, is lowered by penetrating into the barrel (3) in an approximately central position and by immersing in the substances to mix; then said mixing roller (13) mixes by the combined action of its own rotation and the rotation of the barrel (3), moving during said operation towards the periphery, on approaching the walls of the barrel (3), so as to subject the substances to be mixed to crushing, lamination and stretching in all the regions of the barrel (3); finally the mixing roller (13) again takes a substantially central position and in this position it is raised outside the barrel (3) to allow it to move away. Mixing device according to claim 1, characterized in that, in one embodiment, it comprises only a mixing roller (13 '), which preferably has a diameter close to half the diameter of the barrel (3) containing the substances to be mix. Mixing device according to claim 1, characterized in that, in one embodiment, it further comprises at least one second mixing roller (13), parallel to the first roller and supported at a variable distance therefrom. Mixing device according to claim 1, characterized in that it further comprises a cleaning device (16) suitable for co-operating with said mixing roller (13) during its extraction from the mixed substance, to detach from it at least most of the substance remained adherent to said roller (13). Mixing device according to claim 1, characterized in that it comprises a tank (17), disposed in the vicinity of the working position provided for the barrel (3), containing a solvent or a detergent, in which the mixing roller can be lowered after the mixing operation. Mixing device according to claim 5, characterized in that said tank (16) also contains cleaning means, such as brushes or the like. Mixing device according to claim 1, characterized in that it comprises a frame (1), a conveyor means (2) supported by said frame (1) for the drums (3) of substances to be treated, a rotating platform (4) for the barrel (3) being treated, a support plate (8) supported by the frame (1) in contact with the mouth of said barrel (3), a console (12) movable in vertical direction under the action motor means (10,11) relative to said support plate (8), on said console (12), at least one carriage (14) supporting at least one mixing roller (13), motor means (10,15 ) for actuating said mixing roller (13) and motor means for horizontally moving said carriage (14). Mixing device according to claims 5 and 7, characterized in that it further comprises means (7) for moving said support plate (8) in a horizontal direction perpendicular to the direction of movement of said carriage (14), from and to said tank (17) containing a solvent or a detergent. Mixing device according to claim 7, characterized in that at least a part (10) of said motor means is constituted by electric motors actuating maneuvering screws (11). Mixing device according to claim 7, characterized in that sealing means are arranged to act between said support plate (8) and the mouth of the barrel (3). Process for mixing substances 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) allowing it to rotate about a vertical axis and to be raised and lowered in and out of a cylindrical drum (3) containing the substances to be mixed , as well as being moved in the radial direction in said cylindrical barrel (3); means (4) for supporting said cylindrical barrel by allowing it to rotate about a vertical axis; and motor means (5,10,15) for actuating said movements of the mixing roller (13) and of the barrel (3); characterized in that said mixing roller (13) and said barrel (3) are rotated; said mixing roller (13), first raised to allow the installation of the barrel (3) containing the substances to be mixed, is lowered by penetrating into the barrel (3) in an approximately central position and by immersing in the substances to mix; then said mixing roller (13) performs the mixing by the combined action of its own rotation and of the rotation of the barrel (3), moving during said operation towards the periphery, on approaching the walls of the barrel (3), so as to subject the substances to be mixed to crushing, lamination and stretching in all the regions of the barrel (3); finally the mixing roller (13) again takes a substantially central position and in this position it is lifted outside the barrel (3) to allow it to move away. Method according to claim 11, characterized in that said mixing roller (13) is cleaned by a cleaning device (16) during its lifting after each mixing operation. A method according to claim 12, characterized in that said mixing roller (13) is subsequently cleaned by immersion in a tank (17) containing a solvent or a detergent and optionally cleaning means. Barrel intended to be treated in a mixing device, characterized in that its flow opening, arranged in the bottom (19) of the barrel (3), consists of a large opening, normally closed by a conical valve (20) or flat and which can be opened in the form of a relatively thin and extended slit, to take the mixed substance from the barrel (3), in the form of a laminar jet. Barrel according to claim 14, characterized in that said conical or flat valve (20) is pushed into the closed position by an elastic means (21) whose push is overcome by the pressure of an expulsion means (18) used to drain the contents of the barrel (3).

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