APPARATUS AND PROCESS FOR MIXING GRANULES AND/OR POWDERS AND/OR LIQUIDS IN RUBBER PRODUCTION PLANTS

An apparatus and process or mixing granules and/or powders and/or liquids in rubber production plants, including: a mixer/extruder device for the production of a basic heterogeneous mixture; a plurality of distribution lines associated with said mixer/extruder device to supply the device itself with respective powdered and/or granulated and/or liquid products; the mixer/extruder device mixing the powdered and/or granulated and/or liquid products to obtain said heterogeneous mixture; at least one distribution line of a powdered product includes a pre-mixer arranged upstream of said mixer/extruder device to pre-mix said powdered product with at least one liquid product, preferably oil.

The present invention relates to an apparatus and relative process for mixing granules and/or powders and/or liquids in rubber production plants.

In particular, the present invention relates to an apparatus and a method for forming a heterogeneous mixture which is used as a base for the production of rubber in the automotive sector, in particular in the production of tyres, or other related technical sectors.

As is known, in the context of rubber production, materials in powdered form are supplied to respective mixing containers/extruders called “mixers” within which the aforementioned heterogeneous mixture is made.

Such powdered materials, mostly consisting of carbon black, silica and other minor additives such as resins, zinc, clays, stearic acid, are distributed together with oils in pre-dosed quantities through suitable pneumatic supply ducts to the mixer.

In addition, rubber is introduced into the mixer in pieces, obtained for example from the shearing of the rubber obtained from previous processes, to be combined with the powders and oils.

In this situation, the components described above are mixed together inside the mixer and extruded in order to obtain the aforementioned heterogeneous mixture that forms the rubber base.

As described above, all the components are directly introduced into the mixer/extruder and only in this step mixed together.

However, this solution has considerable drawbacks, mainly due to the difficulty of handling very fine powders.

It should be noted that the smaller particles of carbon black, silica and other powdered compounds are difficult to control within the pneumatic supply systems. This entails a major drawback in terms of the amount of material (fine powders) that remains in the systems without being properly supplied to the mixer.

A further major drawback of the known systems is due to the difficulty of mixing all the material to be treated inside the mixer. This drawback occurs because the liquid products (oils) which are delivered in the mixer do not always manage to cover the entire quantity of powdered material. In these cases, in fact, the powders tend to aggregate, thus making it more difficult to properly disperse the oil in a uniform manner.

In this context, the technical task underlying the present invention is to propose an apparatus and relative process for mixing granules and/or powders and/or liquids in rubber production plants, which overcome the drawbacks of the above-mentioned prior art.

In particular, an object of the present invention is to provide an apparatus and relative process capable of dispersing the oils inside the mixer in a more uniform manner, and reducing the dustiness of the components.

In greater detail, the object of the present invention is to provide an apparatus and relative method capable of further aggregating the fine powders before they are mixed with other components, so as to also supply the smallest particles to the mixer.

Furthermore, an object of the present invention is to provide a method for further homogenizing all the components inside the mixer.

The outlined technical task and the specified object are basically achieved by an apparatus and relative process for mixing granules and/or powders and/or liquids in rubber production plants, comprising the technical specifications set out in one or more of the appended claims.

With reference to the appended figures, reference number1globally indicates an apparatus for mixing granules and/or powders and/or liquids in rubber production plants according to the present invention.

It should be specified that the present invention finds advantageous application in the rubber production plants used in the automotive sector, in particular for the production of road tyres. However, the invention can be used in rubber production plants used in various fields, where it is necessary to optimize the distribution and mixing processes of powdered components which are mixed in a heterogeneous compound used as a base in rubber production.

More specifically, the apparatus1which is schematically shown inFIG. 1comprises a mixer/extruder device100for the production of the aforementioned basic heterogeneous mixture.

A plurality of distribution lines101,102,103,104,105are associated with said mixer/extruder device100to supply the device100itself with respective powdered and/or granulated and/or liquid products.

In this way, the mixer/extruder device100, which is not described in detail as it is of known type, mixes the powdered and/or granulated and/or liquid products together to obtain said heterogeneous mixture which is then extruded from the device100itself.

The heterogeneous mixture exiting the device100is then supplied to a subsequent production line (not illustrated, as it is not part of the present invention) adapted to rubber production.

Preferably, in accordance with the preferred but non-limiting embodiment of the present invention illustrated inFIG. 1, two supply lines are provided of respective powdered products101,102, at least one supply line of a liquid product103, at least one supply line of a product in pieces104, and at least one supply line of further additives105which may be in powdered, granular or liquid form.

In particular, a first supply line101provides for the distribution of powdered carbon black, and comprises a series of hoppers “T” to which the product is supplied by means of known supply sources of this material which are not illustrated.

A second supply line102provides for the distribution of powdered silica, and comprises a series of hoppers “T” also adapted to receive the powdered product from further supply sources not illustrated.

The supply line of the additives105has a series of hoppers “T”, each of which is dedicated to the containment and distribution of such chemical additives, generically referred to as chemicals, which may be for example zinc, stearic acid, resins, clay and stearic acid.

InFIG. 1, five hoppers “T” for the above-mentioned chemical additives are illustrated. It should however be noted that the number of hoppers “T” and additives can be different according to the various production needs.

The supply line of the liquid product103comprises an oil tank, which is supplied directly to the device100.

The supply line of the product in pieces04instead comprises a series of shearing devices, also not illustrated as they do not form a part of the present invention, which provide for fragmenting portions of rubber. The rubber in pieces is then supplied inside the mixer/extruder by means of suitable supply systems such as conveyor belts.

The supply lines101,102,103,104and105are also equipped with suitable dosing members indicated by way of example with the reference number106inFIG. 1, suitably formed according to the nature of the product to be dosed to the device100.

The dosing device106provides for delivering dosed parts of the respective products to the aforementioned mixer/extruder device100according to the various production and operating needs of the apparatus1.

Advantageously, at least one distribution line of the powdered product101,102comprises a pre-mixer107arranged upstream of the mixer/extruder device100to mix said powdered product with at least one liquid product. In this manner, the pre-mixer107provides for preparing a mixture of powdered and liquid product which is sent directly to the device100.

In particular, the pre-mixer107is provided for the first supply line101of powdered carbon black. Advantageously, also the second supply line102of powdered silica can also be provided, as indicated inFIG. 1, with the aforementioned pre-mixer107.

In greater detail, the pre-mixer107comprises the hopper “T” for containing powdered products, having on the respective outer surface at least one manifold defining a respective duct “C” in fluid communication with the inside of the hopper “T” (FIG. 2).

At least one blower member1aadapted to deliver a mixing flow of the powders inside the hopper “T” is associated with the duct “C”.

Referring only toFIG. 2, the main components of the member1aare: a hollow element2, a shutter3and an actuator4associated with the shutter3to adjust the position thereof, that is, to adjust the maximum stroke thereof, understood as moving from a closed condition of the shutter to a maximum opening position which can be predefined, as better specified below.

The hollow element2, preferably with a monolithic structure, is a body internally defining a manoeuvring volume for the housing of the shutter3and the passage of the mixing gas flow. In particular, the hollow element2defines therein a duct5configured to pass a flow of gas or other inert gases between an inlet section6and an outlet section7.

The shutter3is contained in the body2to move along a translation axis “A” thereof.

The blower member1afurther comprises a lateral supply duct8which defines the inlet section6and flows into the chamber5in a direction preferably incident to the translation axis “A” of the shutter3.

The chamber5extends between a rear region of the hollow element2, to which the actuator4is applied, and the aforementioned outlet section7.

With reference to the shutter3, it has the shape of a plunger comprising an elongated stem9and a flared or tapered head portion10, preferably frusto-conical. The shutter3is connectable to the actuator4and is positionable with the controlled interruption of the gas flow through the outlet section7.

In particular, a stop element11, having at least one internal stop surface, is arranged in opposition to the shutter3. The internal stop surface, preferably frusto-conical or converging, is counter-shaped to the head portion10of the shutter3to define at least one hermetically sealing configuration of the outlet section7.

The position of the shutter3, controlled by the actuator4, determines the opening and closing of a flow connection between the chamber5and the hopper “T” to which the blower member1ais connected through said duct “C”. In addition, the possible intermediate positions of the shutter3may determine the size of the flow connection passage section. In particular, the size of the aforementioned section is defined by the position of the head portion10of the shutter3with respect to the internal stop surface.

Advantageously, in order to be able to determine the intermediate positions of the shutter3, i.e. the shutter stroke during the opening step, adjustment means are arranged inside the actuator4adapted to determine the amplitude of the output section7.

Such adjustment means may be of a manual type, for a variation of the output section7carried out by manual intervention on mechanical parts of the actuator4, or automatic by means of an appropriate electronic system that intervenes on the actuator4under certain conditions.

The adjustment means therefore allow to control the flow with an “additional” parameter with respect to the ON/OFF pressure and time parameters only (opening and closing of the outlet section7), i.e. a representative control parameter representing the amplitude of the fluid passage section.

Advantageously, this parameter is then controlled (as it is adjusted by manual or automatic intervention) independently of the pressure and opening time parameters of the outlet section7.

The adjustment means therefore allow to intervene on the parameter representing the amplitude of the passage section by optimizing the flow and adjusting it according to the type of material to be mixed, i.e. according to the chemical nature of the material and the particle size of the powders.

Thus, based on each individual mixing step, the individual flow control parameters are suitably independently adjusted in order to optimally mix the powders.

The respective shapes of the head portion10of the shutter3and the internal stop surface and the position of the shutter3may determine the characteristics of the flow of air flowing into the hopper “T” through the duct “C”.

According to a preferred embodiment of the invention, the apparatus1comprises a plurality of blowing members1aof the type described above and associated along a circumferential path at the base of the hopper “T”.

In this way, a series of pulsed mixing gas flows are generated according to a predefined sequence in order to implement a turbulent action adapted to homogeneously mix the powders and liquids contained in the hopper “T”.

In accordance with a first preferred embodiment of the present invention and illustrated inFIG. 2, the blowing member1afurther comprises an injector12for delivering a liquid product directly inside the blowing member1aitself, preferably a mixing oil with the powder contained in the hopper “T”.

In greater detail, as is better illustrated inFIG. 2, the injector comprises an oil supply nozzle13, engaged in an auxiliary duct8aof the hollow element2extending from the opposite side of the lateral duct8and in an incident direction to the translation axis “A” of said shutter.

The injector12is associated with a supply source14of the oil connected to the nozzle13to supply the oil inside the chamber5.

In this way, the oil is supplied directly to the blower member from the nozzle13and conveyed into the hopper “T” by the mixing flow in the form of a nebulized fluid.

As a result, the oil is dispersed in the hopper “T” by means of the vortex flow to significantly reduce the dustiness of the powdered product (typically carbon black or silica) contained in the hopper itself.

In accordance with a further alternative embodiment, the hopper “T” is provided with a nozzle which supplies the liquid product directly into the hopper “T” itself. In this case, the liquid product is distributed on the powders and the gaseous flow generated by the blower member1amixes the powders with the oil to obtain the aforementioned mixture.

Preferably, the aforementioned pre-mixer107can be used for each hopper “T” adapted for the containment of powdered products.FIG. 1illustrates, merely by way of example, pre-mixers107used for the hoppers “T” of the first and second lines101,102respectively provided for the supply of carbon black and silica.

The present invention also relates to a process for mixing granules and/or powders and/or liquids in rubber production plants, comprising the steps of:

arranging a plurality of supply lines101,102,103,104,105of powdered and/or granulated and/or liquid products;

distributing the products inside a mixer/extruder device100; and

mixing the products in the mixer/extruder100to obtain a basic heterogeneous mixture.

The process further provides, prior to the step of distributing the products in said mixer/extruder device, the step of pre-mixing at least one powdered product with a liquid product.

Preferably, a plurality of pre-mixing steps are provided to supply the mixer/extruder device100with a series of powdered and liquid product mixtures.

Each pre-mixing step occurs along at least one respective line101,102, supplying a respective powdered product into the hopper “T” and subsequently delivering a mixing flow of the aforementioned powders into the hopper “T”.

The supply of the powders into the hopper “T” is carried out using known methods.

The step of delivering the mixing flow is implemented by means of the aforementioned blowing member1aadapted to generate the flow of fluid inside the hopper.

In addition, the pre-mixing involves the step of injecting the liquid product, an oil as indicated above, in the mixing flow. Such injection is carried out directly into the blower member in order to distribute the liquid product together with the fluid flow. In this way, the liquid product is nebulized and supplied into the hopper “T” together with the flow to promote, in the vortex motion thereof, the aggregation with the powdered particles.

In accordance with an alternative embodiment of the present invention, the oil is supplied directly into the hopper “T” from above and thus onto the powders. In this situation, the mixing action of the fluid flow still allows to mix the powders and the oil, favouring a homogeneous aggregation.

In this manner, the powder and oil product mixture is supplied directly to the mixer/extruder device100.

The process according to the present invention further provides the steps of supplying oil and sheared rubber directly to the mixer/extruder100together with the additives and the aforementioned mixture.

Note that the apparatus1and the process described above allow to greatly reduce the dustiness of the powdered products intended to be supplied to the device100.

In fact, by means of the action of pre-mixing at least one powdered product with the liquid product (oil), it is possible to aggregate the powders, reduce their dustiness, and thus better control the supply into the mixer/extruder device100.

This results in an optimization in the distribution processes of the products and therefore a reduction in the consumption of the fine powders which in this way are also aggregated and therefore easily moved, and dosed to the device100.

In addition, the action of the mixing flow allows the oils and powders to be mixed in a more uniform manner in the individual hoppers “T” and also inside the mixer/extruder device100.

This results in a better homogenization of all the powdered/granular and liquid products inside the device100.