The present invention refers to an improved fog-generating device.

As known, fog-generating devices are configured to produce, starting from a fog- generating fluid, a very thick fog-generating curtain which completely prevents the vision and are therefore adapted to prevent a theft or a robbery. Such devices, in fact, operate in a few seconds, shooting an amount of steam which, for a few minutes, completely prevents the vision, so that a thief or a robber, lacking orientation, often refrains from proceeding.

Currently, it is provided that, in known fog- generating devices, the fog-generating fluid is quickly evaporated and afterwards condensed into micro-droplets. The size of these droplets is big enough not to be crossed by light without interfering therewith and consequently it causes a diffusion phenomenon (scattering) which precludes the visibility. In order to minimize the chance that a thief completes the theft or causes damages, it is necessary that the environment saturation occurs as quickly as possible: to obtain such result, it is necessary that the fog-generating fluid is entered at an enough pressure and speed into a heat exchanger or boiler of the device, since the quicker the fluid entry speed is, the quicker the steam entry speed is.

Currently, systems for entering the fog- generating fluid inside the heat exchanger ae divided into pressurized systems and pump systems.

In particular, the pressurized systems are based on the use of pressurized containers, which can guarantee a relevant entry speed of the fluid in the exchanger, but have some limits, such as a higher transport cost due to the standards in force, which regulate transports through sea, air and ground for such containers, in addition to certain ratios between pressure and size. Such pressurized containers also have, very often, high manufacturing costs and, in some cases, a complex recharging operation.

The pump systems instead are based on the used of piston pumps with simple effect, directly moved by the field generated by the winding placed around them, for compressing a fog-generating fluid composed of rather fluid mixtures (with strong water percentages) to obtain a rather continuous flow, with few small bubbles and reliable.

The use of such pumps has several limits, such as :

high consumptions, due to the fact that the piston works only during its stroke along one direction;

two valves are necessary;

they are sensible to possible impurities present in the fog-generating fluid, which can make the system partially or totally inefficient.

Moreover, the critical pumping of a fog- generating fluid composed of or based on glycol and its mixtures is due not only to its viscosity and density, but also since, in general, pumps operate as venting devices also at relatively low revolutions (frequency) , and the consequent degassing causes cavitation and loss of efficiency of the pumps.

Moreover, with the current types of pumps, it is not possible to initially modulate the entry speed of the fog-generating fluid (the so-called "soft start") to avoid the "overshooting" effect typical of the initial shooting phase of the steam, since the state, and therefore the flow-rate, of such pumps is rigid, because, due to the supply frequency, of a limited range (50/60Hz) . All this also makes it impossible to regulate the shooting speed .

Moreover, the current types of pumps do not substantially allow the entry of the fog-generating fluid without supply from the electric mains without supply from the electric mains, without using a costly supply stage, since it necessarily requires an alternate current supply.

Document US-A-4 764 660 discloses a fog- generating device according to the preamble of Claim 1.

Therefore, object of the present invention is solving the above prior art problems, by providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which allows simultaneously obtaining a practical use and transport, limited maintenance and chance of quickly entering a high- density fog-generating fluid in the heat exchanger.

Another object of the present invention is providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which, with respect to known systems, allows using a denser fog-generating fluid, with less water, with advantages in density and persistence of the fog-generating curtain.

Moreover, an object of the present invention is providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which, with respect to known systems, allows initially modulating the speed to avoid the "overshooting" effect, typical of the initial steam shooting phase.

Another object of the present invention is providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which, with respect to known systems, allows regulating the shooting speed, for example in order to adapt it to different situations under different use and/or operating conditions .

Moreover, an object of the present invention is providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which, with respect to known systems, allows implementing an automatic procedure for triggering the circuit, should the fog- generating fluid be emptied, without generating steam.

Another object of the present invention is providing an improved fog-generating device comprising at least one mechanical volumetric pump with continuous flow which, with respect to known systems, allows entering fog-generating fluid with strong savings on the electronic board even without supply from the electric mains, since it is also able to operate with direct current supply, coming for example from autonomous batteries.

The above and other objects and advantages of the invention, as will result from the following description, are obtained with an improved fog- generating device as claimed in Claim 1.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a schematic view of a preferred embodiment of the improved fog-generating device according to the present invention;

Figure 2 shows a schematic view of a first preferred embodiment of a component of the improved fog-generating device of Figure 1; and

Figure 3 shows a schematic view of a second preferred embodiment of a component of the improved fog-generating device of Figure 1.

For brevity, herein below the description will be omitted regarding parts and components which are common with prior art fog-generating devices and necessary for the basic operation of the device itself, which are anyway deemed widely known in the art, such as for example electric supply systems, managing systems, gas compressing and channeling systems, shape of boilers and heat exchangers, containers or tanks of the fog-generating fluid, thermal accumulators, etc., to describe in particular aspects and components characterizing the device according to the present invention.

In general, with reference to Figure 1 and as will be described below in more detail, it can be noted that the improved fog-generating device 1 according to the present invention is of the type comprising :

- at least one storage means 3, such as for example at least one tank or bag, of at least one fog- generating fluid to be vaporized, such fog- generating fluid being, for example, glycol or one or more mixtures containing glycol or a glycol base;

- at least one heat exchanger 5 configured for quickly releasing thermal energy, such thermal energy coming for example from a thermal accumulator or boiler (not shown) , to such fog- generating fluid to produce steam V to diffuse in the external environment through one or more delivering means 7;

- pumping means 10 of such fog-generating fluid from the storage means 3 to the heat exchanger 5.

Advantageously, the pumping means comprise at least one mechanical volumetric pump 20a, 20b with continuous flow configured for receiving as input at least one flow of fog-generating fluid FN coming from the storage means 3 and emitting at least one flow of the pressurized fog-generating fluid FN' towards the heat exchanger 5.

In particular, with reference to Figure 2, it is possible to note that, in a first preferred embodiment thereof, the mechanical volumetric pump 20a with continuous flow can comprise at least one compression chamber 21a equipped with at least one inlet duct 22a of such flow of fog-generating fluid FN coming from the storage means 3 and at least one outlet duct 23a configured for emitting the flow of pressurized fog-generating fluid FN' towards the heat exchanger 5, such compression chamber 21a being internally equipped with at least one rotor 25a eccentric with respect to the compression chamber 21a and rotating according to a rotation direction R, such rotor 25a being equipped with at least one radially moving blade 27a configured for cyclically and progressively dividing, during the rotation R, the compression chamber 21a into at least one portion of depressurized chamber 29a placed upstream of the blade 27a with respect to the rotation direction R, and at least one portion of pressurized chamber 31a placed downstream of the blade 27a with respect to the rotation direction R.

With reference to Figure 3, it is possible to note that, in a second preferred embodiment thereof, the mechanical volumetric pump 20b with continuous flow can be of the type with gears and comprises at least one compression chamber 21b equipped with at least one inlet duct 22b of the flow of fog-generating fluid FN coming from the storage means 3 and at least one outlet duct 23b configured for emitting the flow of pressurized fog-generating fluid FN' towards the heat exchanger 5, such compression chamber 21b being internally equipped with at least one pair of toothed wheels 25b, 27b mutually engaging and rotating according to two opposite rotation directions R' , R' ' .

The geometries of the above described mechanical volumetric pumps 20a, 20b with continuous flow 20a, 20b of the device 1 according to the present invention advantageously allow having a big volume of fog-generating fluid also with a number of revolutions low enough not to incur in degassing due to sonication, even with neglected percentages of water inside the mixture of the fluid itself, above all in case of pumping a fog-generating fluid composed of one or more mixtures of glycol or a glycol base.

Moreover, the above described mechanical volumetric pumps 20a, 20b with continuous flow of the device 1 according to the present invention allow their actuation through a motor supplied with direct current which, in addition to allowing the above described functionalities, also brings about the following advantages:

with an amperometric control on the direct current motor, it is possible to immediately detect anomalies, such as from sabotage or clogging of the delivering means 7, or the end of the fog- generating fluid inside the storage means 3, without the need of adding sensors dedicated to such controls;

reliable operation even without supply from electric mains, since the direct current motor can be supplied by a simple battery, without the need of using inverters or oscillators;

no valves are necessary;

use of one or more mechanical volumetric pumps 20a, 20b with continuous flow connected to one or more non-pressurized storage means 3 such as a tank or a plastic bag, containing the fog-generating fluid and possible respective one or more check valves being interposed;

high reliability and life;

sizes of such mechanical volumetric pumps 20a, 20b with continuous flow comparable with those of the current pumps used in known fog-generating devices .

The improved fog-generating device according to the present invention, through the advantageous use of the mechanical volumetric pump with continuous flow as previously described, further allows regulating the shooting speed in order, for example, to adapt it to different situations under different use and/or operating conditions, such as: adapting it to the environment to be protected in terms of more/less speed or more/less steam delivery time;

adapting to heat exchanger conditions, for example when the temperature of the heat exchanger itself is not optimum, due to an absence of supply, or for the need of totally exploiting the energy contained therein;

adapting to the load loss typical of the exchanger directly related to temperature.